Unfortunately, information theory is not a topic that can be made accessible without several nontrivial prerequisites. This would normally constitute a graduate level topic - something to dig into after you've worked through the better part of a mathematics undergrad (particularly the upper level analysis/probability/algebra courses).

Mathematics has a peculiar habit (to those outside the domain) to call things like this "introductions" - it's technically true, but unhelpful to those outside the target audience. Unless you dilute the topic to the point of unusability, this is basically what an introduction to the subject looks like.

Still, it's a little hard for me to figure out what the target audience for this is. Grad students would probably want a focused textbook, so I'm guessing this is for undergrads who are only partially through the full prereqs, but who have a lot of interest in it.