This book has been out of print as an Oxford Logic Guide for a while; and I was intrigued when it was reprinted by Dover. This is a very well thought through and clear account of set theory and some of its models. The treatment of Goedel's definitional model of set theory and Cohen's technique of forcing are the clearest I have come across, although the treatment of forcing is unusual in that forcing conditions are treated as part of the semantics of a modal logic, called S4, rather than being treated as a Boolean logic or as distinct forcing semantics. Personally I think the use of S4 is a step forwards in understanding forcing, as Smullyan and Fitting's translation from classical logic into S4 applied to set theory is syntactically elegant and natural. This is an excellent book all round, which I would recommend, to logicians especially.