I want to recommend a great book that I read over and over and still enjoy. Sadly, it is out-of-print, but maybe you can find it at a library or used book dealer. The book is Cassell's Colloquial Spanish, by A. Bryson Gerrard, published by Collier Books. My copy is dated 1980.
The book is laid out like a Spanish to English dictionary, but only includes words that are "amigos falsos" or otherwise require more explanation than is given in the dictionary. Regional differences in usage are clearly laid out, and it does not include "slangy" expressions that are likely to be out-of-date by the time you get around to using them. Best of all, the author writes in a droll, very British style that I, as an American, find very amusing and entertaining.
For example, this is the first paragraph of the entry on cabrón:
"Included chiefly as a warning; literally 'he-goat' but it has extended from there to 'cuckold' and thence to 'bastard'. It is one of the strongest and rudest words in the Spanish vocabulary; to call a person un cabrón is the equivalent of calling him a bastard or worse. Say it to a man's face, in anger, and you are likely to have a fight on your hands; in some circumstances even a knife in your back."
Does anyone else have great learning books to recommend'