I scanned through your link. Vipassana is covered in chapter 7. That book is actually not the sequel, but more like a previous version of the same material. Altered States of Consciousness could be considered a sequel to States of Consciousness.
The one thing which he presents very clearly is the different mechanics of the different schools which he classifies as concentrative (e.g. concentrating on a mantra like in Transcendental Meditation) and opening up (e.g. as is done in vipassana or in Zen). There is a third category, expressive (e.g. this is done by the Whirling Dervishes) which he mentions but I have not seen him describe those methods in as much detail. These catagories were introduced by Naranjo and Ornstein in On the Psychology of Meditation (out-of-print, can be hard to find, and is not often referenced).
Tart has his own theory for what consciousness is, what an altered state of consciousness is, &c which I do not endorse. I feel it is too simplistic. And his teaching device of the "simulator" may induce groans--he does not demonstrate any mastery of the AI or robotics literature if you ask me.
Nevertheless, on the narrow topic of meditation, he is about the closest thing to an accessible western expert that we now have.
Oops. After checking, I find gwern has the sequence correct and my posts have an error. States of Consciousness is the sequel to Altered States of Consciousness. The one at gwern's link has the most up-to-date data.
Related to: The Trouble With "Good"
Followed by: Vipassana Meditation: Developing Meta-Feeling Skills
I describe a way to understand vipassana meditation (a form of Buddhist meditation) using the concept of affective judgment1. Vipassana aims to break the habit of blindly making affective judgments about mental states, and reverse the damage done by doing so in the past. This habit may be at the root of many problems described on LessWrong, and is likely involved in other mental issues. In the followup post I give details about how to actually practice vipassana.
The problem
Consider mindspace. Mindspace2 is the configuration space of a mind. Each mental state is identified with a position in mindspace, specified by its description along some dimensions. For human mindspace the affect of a mental state is a natural dimension to use, and it's the one that's most important for a conceptual understanding of vipassana meditation.
According to vipassana meditators, every time we pass through a point in mindspace we update its affect by judging3 whether that mental state is good or bad. On the other hand, the path we take through mindspace is strongly determined by this dimension alone, and we tend to veer towards clusters of positive affect and away from those with negative affect. The current judgment of a mental state is also strongly determined by its present affect. This can result in a dangerous feedback loop4, with small initial affective judgments compounding into deep mental patterns. It seems that this phenomenon is at the root of many problems mentioned here.5
Aside from causing systematic errors in thought and action it is claimed that this mechanism is also responsible for our mental suffering and restlessness. Vipassana aims to solve these problems by training us to observe and control our affective judgments, and break out of the pattern of blind reaction.
How it works
There are four aspects to the process:
They are synergistic practices and should be developed simultaneously. This will only be possible later on; at any given time you may only be able to practice one or more of them.
1) Slowing the flood
The ability to calm the mind and concentrate is essential. Without this, one remains involved in the rushing pattern of affect perception and judgment, and there is no possibility of seeing the process and ultimately changing it. This ability is trained by having one maintain awareness of a neutral mental process, which serves as an anchor that one continually returns to. Gradually one becomes aware of the subtle pattern of affective judgments and can distinctly observe them.
2) Not compulsively judging
While periodically returning to the mental anchor, one attempts to observe the mental states that arise without making affective judgments about them. In trying to do this it becomes clear how such judgments can cascade and create deep mental paths that it can be hard to escape from.
3) Smoothing old emotional gradients
Applying this new skill of neutral observation, one works on the long task of undoing old emotional gradients. When observing a mental state without making an affective judgment one can lower6 its present affective value. This is opposed to the previous pattern of making another affective judgment in the same direction, and increasing (or sustaining) its affect. A great variety of mental states will arise during this process, and by neutrally observing them one slowly dismantles the affective structures that are widely distributed in mindspace.
4) No longer forming strong emotional gradients
While smoothing old emotional gradients one must take care not to create new ones. The goal is not to never make affective judgments (I'm not even sure this is possible), but rather to take control of the process and prevent dangerous feedback patterns from occurring.
Conclusion
Vipassana meditation aims to change the way we assign affect to mental states, and reverse the damage accumulated from doing so poorly in the past. Our default way for doing this may be the root of a number of rationality problems. Vipassana serves as a meta-tool, helping one to defuse harmful affective structures that are causing particular problems. I expect that these are common but vary in intensity, and the benefits of vipassana are obtained mainly through correcting these "pathologies".
1 My basis for using this concept is mainly introspective observation during my daily meditation practice the past three years. At the very least I expect it will be helpful for understanding and practicing vipassana meditation, but it may turn out to be a fundamental cognitive process.
2 Note that this concept is distinct from mind design space. In mind design space each point corresponds to a possible mind, and hence each point has an associated mindspace.
3 For a simple case where the distinction between making an affective judgment and not making one is clear, consider experiencing a painful sensation. I claim that this pain is actually a composite phenomenon; it consists of a strong negative affective judgment (or series of such judgments) and a physical sensation. Not making an affective judgment in this case would mean that all that remains is the physical sensation. You would keep experiencing this physical sensation but not have a dying urge to do something about it (like shift your sitting position, for example). As long as you make sure that you are not causing bodily damage, I think that observing pain in meditation can be a really great learning experience.
4 In Buddhist literature the positive feedback spiral is called craving and the negative one is called aversion.
5 Don't forget this and this. This phenomenon may also be responsible for the cached thoughts and cached selves problems, depending on the degree to which cached mental structures are implemented as emotional gradients.
6 This is meant in the sense of absolute value.
Edit: On Academian's recommendation I've added a footnote attempting to clarify the notion of an affective judgment, and what it means not to make one. It's an excerpt from my comment here.