I just purchased Avrukh's book after reading reviews (Silman, Watson, Donaldson) and I'm impressed with its depth as well as the lines given. Unlike in many books where upon further analysis with engines or databases (engine books are useful too) many lines seem to easily go to equality, the reverse often occurs here. The engines and databases start with reasonable scores for Black but soon show the position deteriorating. Although Avrukh's lines are not usually the sharpest and most critical, they squeeze Black without letting go.
However, I'm a bit confused on one variation (p. 128):
1. d4 Nf6 2. c4 e6 3. g3 d5 4. Nf3 dxc4 5. Bg2 a6 6. O-O Nc6 7. Nc3 Rb8 8. e4 Be7 9. Qe2 Nxd4 10. Nxd4 Qxd4 11. Rd1 Qc5 12. e5 Nd7 13. Ne4 Qb5 14. Bf4 O-O 15. Rac1 Nb6 16. Qg4 Kh8 17. Bg5 f5 18. exf6 gxf6
Avrukh gives 19. Bh6 which seems fairly unclear to me despite the weakened kingside. Rybka, Fritz, and the other engines I used give:
19. Nxf6 Rxf6 20. Bxf6+ Bxf6 21. Rd8+ Bxd8 22. Qd4+ Bf6 23. Qxf6+ Kg8 24. Qd8+ Kg7 25. Qxc7+ Nd7 26. Rxc4 with a close to lost position. Perhaps Nd5 is an improvement over f5? It looks gloomy.
Another interesting aspect of this book is the subtlety of some lines. Before reading this book, I would have put some of these positions in an engine and just decided there was nothing in them. Now, I can see that a subtle h3 instead of g3 in the Slav or an unassuming Bd2 can really cause problems if followed up precisely. It has actually scared me since I see how deceivingly difficult these moves can be for the second player. Now, I'm wondering if the Nimzo-English is really acceptable after seeing how Avrukh can use the bishop pair so effectively at times.
Unfortunately, some of the reasoning behind the moves is still not in my grasp (I'm Class A not master). Moreover, there is frequently only one move to fight for advantage - as even engines will claim but since the positions are mostly closed, it seems like White has a lot of reasonable moves. This actually makes the repertoire more difficult to play well than even some super sharp Moscow line in the Semi-Slav. The upside is that players below master strength will probably be equally confused as Black and not even realize their positions are getting worse. Since this book is meant for strong players, I understand why Avrukh refrains from explanations but sometimes the lines are still over my head. On the other hand, if he did this more seriously, it would be another 100 pages. (I wouldn't mind! He's a better writer than he realizes and prose is easy to read.

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I've also noticed a few relevant omissions for Black in less critical systems, as Watson showed here:
http://www.chesscenter.com/twic/jwat91.html but perhaps he just doesn't consider them strong enough to be included. I'm not sure, I've only gone through the book a few hours and these are just impressions.
Anyway, to sum up, the book is an excellent analytical work with deep insight into theory. On the other hand, it provides little commentary and more often that's just something like "Black's most popular continuation by far and best." Still, with some work, the reasons can be worked out from the moves in the main line and his criticism of side-lines. If you play his repertoire already or want to try a solid but positionally rich repertoire, this is highly recommended. Personally, I find these sorts of lines difficult to play with either color and do better with more forcing moves like e4 against the QGA and Bg5 against the Slav. The nuances in these sometimes Karpovian lines are mysterious to me and I have little experience in such positions. Thus, I want to adopt most of this repertoire to become a more complete player. Once the proper study and understanding is in place, I'm sure it will be quite effective. I'm already looking forward to the second volume. I expect to once again be impressed by how apparently non-threatening lines like the fianchetto against the Modern Benoni can be turned into powerful weapons.