Sandman wrote on 10/26/20 at 11:11:05:

You're welcome, and thanks for the compliment!

Actually one other source you might consider has just come to mind, and that's Marin's three-part Grunfeld database for Modern Chess. You'll find it here:

https://www.modern-chess.com/en/chess-databases?database_author=&database_openin...

It aims to present a complete repertoire, it's reasonably up-to-date (2017) and like most of Marin's work, is thoughtfully put together and contains some illuminating explanations, which might suit your needs.

Fling is referring to the older Delchev/Agrest book, which has been superseded by the new edition (by Delchev only) that came out earlier this year. Yes, it does offer a complete repertoire, but as I mentioned upthread, it has gaps in it and I would not feel comfortable relying on it. Let me illustrate this point with an example to give you some idea of what I mean.

Against the Russian System (1.d4 Nf6 2.c4 g6 3.Nc3 d5 4.Nf3 Bg7 5.Qb3), Delchev recommends the Hungarian Variation, which goes 5...dc 6.Qxc4 0-0 7.e4 a6. This has been very popular at higher levels over recent years, so there's a lot of theory and play can become extremely sharp. 8.Be2 is usually played nowadays, but 8.e5 used to be the main move and is very dangerous. Delchev says about the latter: 'Nobody from the top seems to be playing 8.e5 any more'. He then gives a lightly annotated illustrative game over half a column to deal with this line. Kovalchuk, by contrast, takes nearly 30 pages to delve into the complications that ensue, which Delchev leaves Black completely unprepared for. I suggest you have a quick glance in a database at, for example, the uncompromising line that goes 8...b5 9.Qb3 Nfd7 10.h4 c5 11.e6 and decide whether you'd be happy to wade into this mess with no preparation whatsoever – because Delchev doesn't even mention it. He's right that this isn't played at the top level any more, but even just this subvariation (up to 11.e6) has featured in many strong-GM games over the years, and it's exactly the sort of thing an attack-minded club player might throw at you. Of course, you can try to work it out over the board, but if you're left to fend for yourself in a line like that, then I'd argue that your repertoire book hasn't done its job very well.

EDIT: for clarity and to insert missed-out move.

@seeley, that’s very informative and I do appreciate the extra insight as well. I toyed with the Grunfeld back before my break (family, daughter’s sports, that darn work, etc) without any in-depth study and I enjoyed it. Now I’m back and thought I’d try it again. 

@pawnpusher thank you for your thoughts as well. Why do you prefer Kovalchuk over the others?

Although Jonathan Rowson's work Understanding The Grunfeld (1999) is now hopelessly out of date in theoretical terms, it remains, in my opinion, far and away the best introduction to the Grunfeld if you're after verbal explanations and discussions of themes. Playing The Grunfeld (2020), by Alexey Kovalchuk, is both well-researched and thorough, as well as being up-to-date, and is the one I'd recommend out of the recent rash of books on the opening. Between them, they will offer you a good grounding. Delchev's The Safest Grunfeld Reloaded (2020) is also worth getting and contains many interesting and original ideas. However, it has gaping holes in its coverage, and I certainly wouldn't want to rely on it for a complete repertoire.

I know this wasn't the question, but as a club player coming back to chess after a ten-year break, with, presumably, lots of other bits of work you plan to do on your chess, you might want to consider taking up a less theoretically demanding opening than the Grunfeld at this stage. I've played it for thirty years, and though I love it, I still walk into the occasional sucker punch, where I've forgotten some obscure bit of theory that I haven't looked at for a long time, and when that happens in this sharp and unforgiving opening, you can be pretty much lost immediately. Unless you're professional or have a huge amount of time to spend on your chess, that's highly likely to happen to you too, and it can be quite demoralising. If I was starting out again today, but knowing what I do about the Grunfeld, I'd certainly take up something with a greater margin for error as my main Black defence to 1.d4.

For explanations, Understanding the Grunfeld by Rowson is a favorite of mine. But Delchev's and Agrest's book also has good explanations, and is more complete in terms of a repertoire than Rowson's book. I haven't followed the Grunfeld much, though, so I can't really tell if there are any glaring holes in D&A's Safest Grunfeld.

"The Grünfeld according to Svidler" series of videos on chess24.com