Alternate Reference for Topological K-theory

I have been trying to read Atiyah’s Topological K-Theory. The book, in general, is quite painful to read as the proofs are in most cases too precise for the first reader to understand, and lacks to motivate the topic properly.

I would like to know if there are better books which are aimed for a first reading of Topological K-theory which doesn’t assume the knowledge of vector bundles. Even very well written lectures notes will suffice for me.