most comprehensive endgame reference?

Nothing is more comprehensive than the eight volumes edited by Averbakh.

Nice! Are they in English? Mine are in Russian, so I only looked at the diagrams.

Yes. All in English translation. Published in the 1970s by Batsford in England and Chess Digest in the US.

@23

They contain errors.

All books contain errors. The real question is:

Are the errors significant enough to discount the relevant value of the book? Probably not.

Back in the 1990s some people fed Rueben Fines Basic Chess Endings into a computer to determine the accuracy of the material. They found that it was 96% accurate. Pretty good for a lone man at a typewriter in 1943.

@25

"Are the errors significant enough to discount the relevant value of the book?"
++ Yes: Dvoretsky or Müller & Lamprecht are engine checked.
Checking Averbakh against the 7-men endgame table base reveals many errors: false evaluations, wrong lines. Why recommend something known with errors, when better is available?

But, these are far from comprehensive. I love Dvoretsky. No book has done more for my endgame, but Dvoretsky cannot pack into one volume what Averbakh and others (Chekover, Maizelis, Levinfish, …) presented in eight volumes.

For rook endings, a better choice might be the two volumes published last year. Theoretical Rook Endgames by Sam Shankland and Conceptual Rook Endgames by Jacob Aagaard. These are more thorough than Levinfish and Smyslov, Rook Endings in the Averbakh series, as well as more recent work by Dvoretsky, Müller and Lamprecht. They are also checked by computer.

Sam Shankland also has two books on pawn endings.
The OP asked for a comprehensive reference. The Averbakh series as a set remains the most comprehensive single source with instructive text, while Encyclopedia of Chess Endings remains the largest collection of positions.

Perhaps the OP is asking the wrong question.

Reading a section of Ilya Rabinovich, The Russian Endgame Handbook yesterday, I was astounded by the large number of obvious errors in notation. However, none of these interfered with my understanding of his analysis.

I don’t know. I thought it was a different packaging of the same series. Clearly, if Averbakh is the author of the rook volume, it is not the same.

At present, Internet Archive has Comprehensive Chess Endings. This a great service, as the books are impossible to find, but it is also a copyright violation. Internet Archive has been getting pressure to take some of these violations down, so don't count on finding it there.

Well, if you do not mind the less than perfect (Pergamon’s) printing quality, the Averbakh’s 1986 Pergamon Press Series (vol 1 ~ 5) is now re-printing by Ishi Press. If you do a quick search on Amazon dot com, u will find them all. In the Rook Ending (vol 5), there are some (very few) pencil notes which also appeared on the vol 5 internet pdf.

Ishi Press vary from difficult to impossible in print quality. They are not doing anyone a service with their reprints.

I bought seven of the original eight books in the Averbakh series two years ago. Prices ranges from $10 to $25 per volume. I already had Rook Endings. I bought some from a guy on Chess Book Collectors on Facebook. Some through booksellers using ABE Books.

A friend recently offered to sell me the Pergamon series. Maybe, if someone is interested, I can put them in touch. The series has decent printing quality, unlike the Ishi reprints.

The Fine book also is known to have many errors. It was intended more as a reference book than a training manual.

Keres’s Practical Chess Endings is more user-friendly than Fine’s book and I think is a better instruction book.

my vote is for the Dvoretsky book as a reference.

As training books, I recommend Chernev’s Practical Chess Endings for beginners and de la Silva’s 100 Endgames you Should Know for 1700+ players.

Silman's book is probably good for beginers. Also, very interesting is https://shop.chessbase.com/en/products/mueller_endgames_1_to_14. Dvoretsky's endgame manual is too advanced - master level. Fundamental chess Enginds is also OK.

The “relationship” between the Batsford series and Pergamon series…….

1. the Batsford series was planned to have 8 volumes, however, only 7 were released. The Rook Endings one was never published. The 7 volumes published by Batsford are: a) Pawn Endings, b) Knight Endings, c) Bishop Endings, d) Bishop vs Knight Endings, e) Queen Pawn Endings, f) Queen vs Rook/Minor Piece Endings and g) Rook vs Minor Piece Endings. After Pergamon took over, these 7 were released in 4 volumes: Vol 1, Bishop Endings and Knight Endings (b+c); Vol 2: Bishop vs Knight, Rook vs Minor Piece (d+g); Vol 3: Queen Pawn, Queen vs Rook, Queen vs Minor Pieces (e+f); Vol 4: Pawn Endings (a). Vol 5: Rook Endings (not published by Batsford).

2. Batsford series is in Descriptive Notations, Pergamon series is in Algebraic.

More info on the Pergamon series: the first impression of vol 1, 2 HC version were printed in Hungary with inferior paper, comparing to vol 3 ~ 5.

I actually bought the Ishi reprints, but decided to sell them all last month when I saw a seller on eBay selling Pergamon vol 1~4 with reasonable price. I believe the same seller put yet another Pergamon set of 5 in mint condition for sale on eBay now.

Recently, I emailed Quality Chess about their intention to issue a whole series reprint, but GM Aagaard (co-founder of Quality Chess) told me the following:

”Hi Steven,

I think the series would need a massive revision. I will bring it to the team, but I doubt it has great interest at this moment.

Jacob”.

I suppose the rook endings one was not published because the volume by Smyslov and Levenfish was already out in English translation.