On Lisp

by Paul Graham, which is what I am reading atm. Sadly it is out of print so your options of obtaining it are basically limited to buying a used one via ebay or flea-markets, borrow it from a library or simply stick with online version, for free.

I think it's a great book, because it delivers what the cover promises “Advanced Techniques for Common Lisp”. Though i find his usage of destructive functions a bit strange, he says one should treat them as if there were a tax on their use, but he uses them in almost every function he defines.

I found a well-preserved copy of CLtL2 for € 12.50 on ebay, but it the last minutes it went up to € 25, too high for me now :(