Reference:
Collins Bradford's Crossword Solver's Lists
Anne Bradford books are considered a must-have for all aficionados of the cruciverbal form (the crossword, that is).
Collins Bradford's Crossword Solver's Dictionary
Here’s her dictionary – a cheater’s dream. Don’t peek unless you really have to!
Chambers Crossword Dictionary
More cheating, from the great tomes of Chambers
Ximenes on the Art of the Crossword
Well, many cryptic setters regard this as their Bible. This is a fascinating read. Ximenes was the first to lay down the rules of good crossword clues, and succeeding generations of setters will choose whether or not to abide by them!