I enjoyed
The Witches of Karres. It's ideal for a Harry Potter crossover, because the governments in both series are net drags on
everything. (I'm extrapolating here. There are four Karres books, but James H. Schmitz was only involved with the first one.)
Another book you might enjoy is
The New Hacker's Dictionary. It can be downloaded from the net. Available as
HTML, on the
Wayback Machine (apparently not downloadable), in
a number of formats at Manybooks. (They also have the first edition.) I appreciate the book, because I was there during its formative years. I visited the Tech Model Railroad Club. I programmed the IBM 704. I played the original
Spacewar on the PDP-1, and when I graduated and went to the University of Minnesota, I rewrote it from scratch to run on the CDC-3100. Then I sold the article to John W. Campbell.
Note that this book was assembled by the folk process, with the folk in question being hackers. As Eric Raymond said:
"This document (The Hacker's Dictionary) is in the public domain, to be freely used, shared, and modified. There are (by intention) no legal restraints on what you can do with it, but there are traditions about its proper use to which many hackers are quite strongly attached. Please extend the courtesy of proper citation when you quote the File, ideally with a version number, as it will change and grow over time. (Examples of appropriate citation form: "Hacker's Dictionary 4.3.0" or "The on-line Hacker's Dictionary, version 4.3.0, 30 APR 2001".) "
Or, if you feel like it, you can buy it at Amazon, or some other book store.