I am re-reading the Hartson book right now.
Well written, can be digested in small portions (2 page lessons)
My biggest find has been Irving Chernev - Logical Chess Move by Move
This is the book I have been looking for all my life. Annotated games with every move explained not just "Black has the advantage" after 11 moves !!
John
Gligoric's 'I play against pieces' isn't bad.
Its a collection of annotated games, grouped by opening. However, these are supplemented by details of what was happening to Gligo at the time.
Its particularly interesting if you're a 1.d4 player - many of the opening ideas in these lines are very well explained.
I've just bought Dvoretsky's Endgame Manual. Looks very good, but I've only skimmed through it.
I'm reading 'How to play chess endings, by Eugene Znosko-Borovsky, which is very literate and entertainingly written. I think he's written books on the middle game and the opening aswell. He talks about general principles instead of just going through moves. There is another great book called 'The Complete Chess Addict'- can't remember the name of the author.