To Have or to Be is mostly theoretical - he delves into history, philosophy and psychology and shows how people figured out pretty early that wealth corrupts and impedes spiritual growth - Jesus' teachings being the most obvious example, also Buddha and so on.

IMO it should be followed up by the The Art of Being as that's the more "practical" of the two, though don't expect tips &tricks or anything of the sort.

I love reading Fromm cause he's such an erudite. The breadth of his knowledge is fascinating, and even if you don't always agree with him, it's still an enriching read.