:santagrin: This book was suggested by John Pinto

Excerpts from the Book Description:

A classic exposition of a branch of mathematical logic that uses category theory, this text is suitable for advanced undergraduates and graduate students and accessible to both philosophically and mathematically oriented readers. Robert Goldblatt is Professor of Pure Mathematics at New Zealand's Victoria University.

Reviews:

Amazon.com

:) "The book is well written, accessible to graduate students, filled with fun and often challenging exercises, and packed with references. In my opinion, it is the right place to start if you want to become proficient in topos theory (and you don't already have significant proficiency in category theory)."

:) "To put it bluntly, Goldblatt strikes me as a superior mind, even his brief remarks on set theory were enlightening."