The Ultimaye Gambit Guide

Nigel Davies wrote Gambit Opening Repertoire and Gambit Opening Repertoire II. The first is for White, the second for Black. I know the latter covers a Black repertoire using the 3...f5 Ruy Lopez and Albin-Countergambit. The theory is about 20 years old, and it's unsound.

WHITE

https://www.amazon.com/Gambiteer-Hard-Hitting-Opening-Repertoire-Everyman/dp/1857445163/ref=sr_1_26?crid=3G4B61LBZCV70&dib=eyJ2IjoiMSJ9.2B_fg69-q5WEy-t_xv90Tl8Lus4dFijW_vO7aSYQOs417qzg-hh1UT8kmwzf-MSeLJxj8t-f-8r7BJNIVaywgtkoCcIssDK70Ndy3ZYrXuiqVlfW99w6T_KZm7tXSz5oBOrTHPWP1tmPxloKzHS09V9y6lcvhn4toVFHH77VnjNNqYAz_i79ZF-DN_8c_udy9ZQXSeNp0isSsuq0HEVO_2IaNOVpMUQkVzvTdrOdbNY.27ShhS_qM_-d9x3XJHgk9top2Xt5W8CfONSndyf_ETc&dib_tag=se&keywords=Nigel+davies&qid=1736053872&s=books&sprefix=nigel+davies%2Cstripbooks%2C97&sr=1-26&xpid=81ExZoHBjR5fh

BLACK

https://www.amazon.com/Gambiteer-II-Hard-Hitting-Opening-Repertoire/dp/1857445368/ref=sr_1_1?crid=2OX0SK7X9F9CH&dib=eyJ2IjoiMSJ9.stUipfI7fUfVugfFshr8xCy0IweLwFv055c36ZnSK6M.RTX2S_4hq2pwfR88D7P_nnSqnz8ETQ1gO0OrosYwp9g&dib_tag=se&keywords=Gambiteer+II&qid=1736053927&s=books&sprefix=gambiteer+ii%2Cstripbooks%2C85&sr=1-1

Avoid "Gambits Accepted" (L. Elliot Fletcher, Routledge 1954). Although it can be of antiquarian interest for the experienced gambit player, it's generally regarded as being one of the worst chess books ever published.

I can name a few in real competition with that book for worst ever written. The former is full of mistakes. The latter is just complete trash and useless.

Case in point for the former (not sure if an "edited" second edition was published, but this is based on the first edition when it came out around the turn of the century.

There is a famous Semi-Slav, Botvinnik Variation game from 1996 between Ivanchuk and Shirov featuring the line where White sacrifices the Queen on g7 on move 21. This same game is also the very first game in Matthew Sadler's book on the Semi-Slav from 1998. The assessment of Shirov's 23rd move is vastly different between the 2 books. I don't recall which of the followinging scenarios is the case, but it is one of the following two cases:

Sadler - 23...d4? And Schiller - 23...d4!!

OR

Sadler - 23...d4?? And Schiller - 23...d4!

One gave two and one gave one, but for Sadler, it was question marks, and for Schiller, it was exclams. No move after 23...d4 was given an exclamation, question mark, or explanation saying how bad or phenomenal any subsequent move was by either player in the game in Schiller's book, and White won on move 35. This is just one of many disgraces in Schiller's book.

So those two books that compete for worst chess book ever written:

1) Standard Chess Openings - Eric Schiller

2) Rapid Chess Improvement - don't recall the author.

I wholly agree with @ThrillerFan - there's many a bad book out there. I seem to recall that Moody's "Evans Gambit Revolution" (1995) also came in for an utterly excoriating review in BCM.