Rolf Nelson's blog, The Rational Entrepreneur has more rigorous content than Paul Graham in the sense that Rolf pays more attention to studies and evidence and so on and has less of Graham's exploratory musings based on personal insight and nostalgia, with the occasional reader ego-stroke. Rolf's content lacks the "ecological credibility" of having personally made a bunch of money off of two successful companies the way Graham has (once is a accident, twice suggests a pattern, the third time confirms the pattern), because Rolf wrote the blog as a way of doing basically what you are doing right now: reading a ton about businesses and startups before jumping in for his first iteration. If you like the blog, you might try contacting Rolf directly as he's an old time OB/LW reader :-)