John, David, Thank you for alerting us to this reading group.
Steve Roman's book is rather expensive on Amazon. He sells directly, as a PDF, for $24.95, at his website
, a book which seems to be an early draft from 2015. The title is slightly different, "An Introduction to Category Theory", the page numbers are different (because the pages are bigger). Both books have exercises. The Table of Contents is similar, but in the final version, at Amazon, he seems to have changed or added a few sections, and reworked the chapter on Adjunctions. So there are some substantial differences, it seems.
The ebook at Springer for his book An Introduction to the Language of Category Theory
is 46 euros, which is cheaper than Amazon's price of 65 dollars.
His book seems very readable.
He also has [six video lectures](https://www.youtube.com/watch?v=If6VUXZIB-4&list=PLiyVurqwtq0Y40IZhB6T1wM2fMduEVe56) which have gotten excellent reviews.