For the Semi-Slav, I would recommand another book from Vigorito: Play the Semi-Slav. As the Vigus one, it's also a repertoire book for Black starting after 1.d4 d5 2.c4 c6

If you want to play for a win, I'd say that below 2200 Elo I don't care too much about the opening. It can be the French Exchange, The Slav Exchange or whatever else, I think you'll have opportunities to win the game if you play better than your opponent.

For higher Elo, I don't know... but I can guess. The Semi-Slav gives probably better oppotunity for a win than the Slav. Paradoxically, I think that the Vigus repertoire's book gives more unbalanced positions than Vigorito's book, at least on common opening. In the Slow Slav with 4.e3, Vigus chooses 4...Bg4 and Vigorito 4...Bf5; in the exchange variation, Vigus' choice is also more provocative (with Nh5) than Vigorito (very symmetrical). Neither choice is better in my opinion, just different. And I'm happy to have both choices, depending on my state of mood and my opponent.

Bottom-line: as repertoire books, both books are great!

In addition, if you want books on the Semi-Slav, there are 2 books I don't know much about. The new book from Dreev (Moscow variation 1.d4 d5 2.c4 c6 3. Nf3 Nf6 4. Nc3 e6 5.Bg5 h6) and an older one from Vera, Chess Explained: the Meran Semi Slav (1.d4 d5 2.c4 c6 3. Nf3 Nf6 4. Nc3 e6 5.e3).

Good luck with the Slav and Semi-Slav!

@ Kobesarmy: I would first read Starting Out: Slav & Semi-Slav from Flear. It's a nice book explaining the main ideas and lines of both openings (plus a small part on the 4...a6 Slav). It gives you a taste if you like the opening or not; and if you like it, which one of the 3 system.

If you already made up your mind with the 4...dxc4 Slav, you can probably skip the Flear book. I would then recommand 2 books: the Vigus book discussed previously (an excellent repertoire book), and also Vigorito's book Chess Explained, The Main-Line Slav. It's not a repertoire book and gives an excellent overview of the 4...dxc4 Slav (without any coverage of the Slow Slav and the Exchange Slav). Both books are very complementary.

Slav players can be happy: there are a lot of great books to choose from!

I am somewhat struck by that assessment of "not mainstream."  I mean, 4...Bg4 in the Slow Slav has long been a major line in the books, and as far as I know, that Sokolov line with ...Nb6 has been pretty popular among GMs for some time now (for instance, just picking up an Informant from about five years ago, there are several games with it).

Black's general idea is usually to go ...Nfd7, exchange the active Ne5 and break with ...e5. For, example - 9.f3 Nfd7 10.Nxd7 Nxd7 11.e4 Bg6 and Black will often aim for ...e5, ...Qb6, ...exd4, ...Bc5 etc. This is the main line, although there are plenty of other options for White, he is by no means limited to 9.f3, for example. Check out some games in your database for specifics.

After 4.e3 Vigus does indeed recommend 4...Bg4 and gives good coverage of it. Though 4...a6, 4...Bf5 and 4...g6 are all perfectly good alternatives, if you prefer one of those.

As a solid, not mainstream, low maintenance, self-contained repertoire after 1.d4 d5 2.c4 c6, its a great book.

It all depends what kind of Slav you're aiming for - Semi-Slav, ...a6 Slav, or the traditional main line Slav (with ...dxc4 and ...Bf5).

If its the latter, and I assume that it is, then Vigus' Play the Slav is excellent. He proposes 1.d4 d5 2.c4 c6 3.Nf3 Nf6 4.Nc3 dxc4 5.a4 Bf5 6.Ne5 Nbd7 7.Nxc4 Nb6 8.Ne5 a5 as his main line recommendation, which is solid, active, and not as forcing as some of the deeply analysed main lines. White has plenty of opportunities go go wrong here. Many of his other recommended variations are not main line, yet completely sound and a welcome change.

If you're aiming for a Semi-Slav or ...a6 Slav, then longer forcing lines are much more common.