I started reading Hubbard and Hubbard's Vector Calculus, Linear Algebra, and Differential Forms a few months ago on the recommendation of a former professor, but I found myself confused both reading the proofs provided and writing the proofs from the exercises. I finally gave up recently, feeling that I simply wasn't getting what I should have out of the book, as I was often skipping the most important parts because I didn't understand them! Thus, I started looking for "Intro to Proofs"-type books. So far, the two I have looked at are The Art of Proof: Basic Training for Deeper Mathematics and Mathematical Proofs: A Transition to Advanced Mathematics. I found the former one to be too focused on justifying every single step with an axiom in proofs for which I feel this was not necessary. The latter I found better, but I simply wasn't interested in the proofs - so many even and odd number problems!
What I'm looking for is something that
(a) will prepare me for the difficult-to-understand proofs in Hubbard and Hubbard
(b) will intrigue me and expose me to new math (new to me, not necessarily new in the world) and interesting problems
N.B. Obviously I would prefer the books be available online, but I understand that this is not always possible.