In 2011 Quality Chess put out a great book on the Tarrasch Defense (the opening that characteristically arises via the moves 1.d4 d5 2.c4 e6 3.Nc3 c5) by Nikolaos Ntirlis and Jacob Aagaard. As is typical for QC books, that work didn't just summarize the theory of that opening but developed it, and while the book was (and is) a useful resource for club players it's pitched for stronger players - around 2000 and up, in my opinion. Also, its scope is somewhat limited. It is a repertoire book (nothing wrong with that), and in the main line with 9.Bg5 the coverage is limited to 9...c4. That's quite enough, as anyone who has the book will know, but there are other interesting lines available to Black as well.
There are thus three reasons why Irish IM Sam Collins' new book on the Tarrasch from Everyman has a useful spot in the market. First, 2-3 years have passed since the QC book's publication, so it's useful to take note of new developments. Second, Collins is aiming not at strong club players and those with FIDE titles but at typical club players. Stronger players will learn something too, but he isn't writing primarily for professional players and wannabes. And third, more repertoire choices are offered, which means that the book is not "Ntirlis & Aagaard for the Masses" but an independent work on the line.
There are other possibilities for White, but I will focus my attention here on the main line arising after 4.cxd5 exd5 (interestingly, Collins takes a little look at 4...cxd4) 5.Nf3 Nc6 6.g3 Nf6 7.Bg2 Be7 8.0-0 0-0 9.Bg5 (9.dxc5 is another big complex). The QC book advocates 9...c4, and after 10.Ne5 Be6 11.b3 put their energy into 11...h6. They mention 11...Qa5 in the Introduction, but think that after 12.Qd2 Rad8 13.Nxc6 (13.bxc4 Nxd4!!) 13...bxc6 14.Rfd1 Bb4 15.Rdc1 (recommended by Lars Schandorff in Playing 1.d4: The Queen's Gambit) promises White an advantage. They also address both the old-fashioned 9...Be6 and the absolute main line 9...cxd4 10.Nxd4 h6, but likewise offer brief arguments for the claim that White has an advantage.
It is these three options that Collins seeks to rehabilitate. Though he does offer a few paragraphs' coverage of the Ntirlis & Aagaard approach with 11...h6 in the 9...c4 line he spends more time on 11...Qa5. Unfortunately, he doesn't directly address Schandorff's line. After 12.Qd2 Rad8 13.Nxc6 bxc6 14.Rfd1 Bb4 he considers 15.Bxf6 gxf6 and now 16.Rdc1, but as it looks like his main line transposes to Schandorff's we can continue. After 16...c5 we transpose to Schandorff's 15.Rdc1 c5 16.Bxf6 gxf6, and now 17.bxc4 dxc4 18.d5 and here rather than 18...Bxd5 (given in Schandorff) Collins proposes 18...Bxc3 19.Qxc3 Qxc3 20.Rxc3 Bxd5 21.Bxd5 Rxd5 22.Rxc4 Rb8, with a version of a typical Tarrasch endgame that's slightly better than usual for Black, but which Collins admits is still "a bit better" for White. A mixed success there, to be sure: it's not as bad for Black as Schandorff suggests, but not as good for Black as the positions Ntirlis and Aagaard achieve, if their analysis is correct.
Next and surprisingly, Collins also plumps for that rare old bird, 9...Be6. Ever since the Yusupov-Spraggett game back in 1989, won in model style by White, theory has frowned on this variation for Black. It is solid but gives White a slight and permanent edge, while Black has no winning chances whatsoever against a decent player who doesn't blunder. Against this, Collins rightly points out that most of us aren't going to be facing Yusupov and that there Spraggett's play can be improved. That's true, but then most of us aren't going to play the endgame even as well as Spraggett did either! Moreover, Collins admits that "Black can't be better!" and "should never win such a position", while White is guaranteed "a small but enduring advantage" and "his position is considerably easier to play." Not exactly a ringing endorsement! That said, if one puts in the time to really understand the position with Black, it could be used as an occasional drawing weapon as needed. Maybe it won't be much fun, but if the experience edge is sufficiently on Black's side of the ledger it might not be so bad.
Finally, there's the main line with 9...cxd4 10.Nxd4 h6. Now 11.Bf4 is a good second approach, but we'll stick to the usual move, 11.Be3. Now 11...Re8 12.Rc1, and here Collins discusses both 12...Bf8 and 12...Bg4. White's #1 reply in the latter case is 13.h3, and Collins examines this, but there's also 13.Qa4. This is less common but has a better score, and is recommended in the intro to the QC book on the Tarrasch. Unfortunately, Collins doesn't address this one. As for 12...Bf8, Ntirlis and Aagaard suggest 13.Na4 Bd7 14.Nc5 Bxc5 15.Rxc5 Qe7 16.Nxc6! bxc6 17.Rc2!N Ne4 18.Qd4 a5 19.Rfc1, with a slight edge for White thanks to the bishop pair and his general harmony. Against this I have some bad news and some good news. The bad news is that while Collins covers that line up to move 15, he doesn't consider 16.Nxc6. The good news is that he offers two alternatives on move 14 and two more on move 13.
In summary, the book does not go into the same depth as the earlier Quality Chess publication, but that's not its function. It is not an exhaustive repertoire book suitable for masters and grandmasters; it is instead an introduction to the Tarrasch Defense for club players that can benefit stronger players, though it is not primarily aimed at them. One nice feature of the book as an introduction to the opening is a "Structural Introduction" early on. It covers six typical pawn structures that can arise in the Tarrasch, and then follows up with a brief discussion of the transportability of Tarrasch lessons to other openings with isolated d-pawns.
The bottom line: I can recommend this book to club players interested in the Tarrasch. If you're a strong club player (or even higher-rated) and can only buy one book on the Tarrasch, you should go for the Ntirlis and Aagaard masterpiece, but if you can I'd recommend buying both books. Being able to play more lines in the Tarrasch is good, both for the sake of variety and to avoid being too stationary a target. I think stronger players will want to supplement Collins' book in a way they might not need to with the QC work, but with that caveat I can recommend it to them too.