I went through most of the Heinlein's Future history series and some other writings. It's very very uneven, even within a single novel. The dialog is often gripping and witty, at other times long and boring. Technical and scientific descriptions tend to ramble on as if it were a textbook or a manual. At his best, Heinlein has several quotable sentences on every page, it his worst, you can skip whole chapters. He generally sucks bad at writing endings, even to otherwise excellent novels.

The Moon is a Harsh Mistress (not generally considered a part of the series) is one of those I liked most. Stranger in a Strange Land was great at tmes, but spoiled by the occult parts and the meaningless (to me) ending. Time Enough for Love is probably the most uniformly well written, if you excise the genetics babbling, though the ending, again, could have been better. Whoever were his editors, they never did a good job. Still, as sci-fi goes, it aged well, except for computer-related references and plot twists.

His rather anarchist and libertarian political ideas did not grate on me. This was a welcome contrast with Ayn Rand, whose novels I found impossible to get through.