Book’s homepage: http://www.mcafee.cc/Introecon/
There seems to be threeish versions about:
The original (the one your link goes to), which McAfee believes may be preferred by the mathematically sophisticated or engineers. This is the one I’m personally using, currently.
A second version, meant to improve accessibility, which McAfee expects professors considering the text to prefer
Version 2.1, which appears to be a refinement of version 2. Includes solutions to exercises, cosmetic improvements, and “small edits for consistency of notation and for clarity.”
(I’m vaguely reminded of Debian-Ubuntu-Mint Linux distros. Yay open source?)
Second the rec on Sadava. I strongly preferred it to Campbell, the other standard intro bio text, which I found insufficiently precise. I’d go to make an Anki card about some concept, only to find that Campbell’s discussion lacked enough precision for me to state exactly what was going on. Sadly, I haven’t read another biology book (having been quite satisfied with Sadava’s), so I can’t make a Luke-compliant recommendation.