Unity 5—From Zero to Proficiency (Foundations) P Felicia. An entire book for what I expected to spend two hours to lecture on.
Programming in Lua, Fourth Edition R Ierusalimschy. Easy to read and understand, good examples.
The biblatex Package—Programmable Bibliographies and Citations P Lehman with P Kime, A Boruvka & J Wright. Somehow it is difficult to figure out exactly what to do just from reading the manual. Reading the source is required.
The Art of Game Design: A Book of Lenses, Second Edition J Schell. One of Randy Pausch’s students. It shows. Good stuff.
C# Programming in Easy Steps M McGrath. Now this was a complete waste of time and money.