There is, of course, the very famous book by Barendregt, which doesn't require much background except for the usual mathematical maturity. He also has some introductory notes here.

There is, of course, the very famous book by Barendregt,

• The Lambda Calculus, Its Syntax and Semantics (Studies in Logic and the Foundations of Mathematics, Volume 103). Revised Edition, North-Holland, 1985. (link to vendor)

which doesn't require much background except for the usual mathematical maturity. This is mostly about the untyped lambda calculus. He also has some introductory notes here.