It slipped under my radar, but +Nathan Irving quietly released his excellent Basic Illusionist a few days ago.
S&W Appreciation Day back in April of 2014. Since then the book has seen some edits and it is now available as a proper DriveThruRPG download.
I talked about this book at length back in May. Everything I said then applies still.
I mentioned a few games it works well with (PWWO) but since that time I have also used it in conjunction with other books.
ACKS Player's Companion
The Gnomish Trickster has a number of good spells that work well for the Illusionist. All the arcane spells tagged as (ill) for illusion would work nicely as well.
Adventures Dark and Deep
This game has both an illusionist and a mountebank classes. Not to mention plenty of spells.
The Companion Expansion
This is another "Companion" style book for Basic-era D&D and clones and is something of a forgotten treasure. It also has an Illusionist Class that is roughly equal with the Basic Illusionist, but the real feature of this book is the expanded spell list. If you are looking to extend your illusionist a bit more with more spells then this is a good way to do it.
Labyrinth Lord Advanced Edition Companion
Given it's aim to emulate AD&D via the Basic D&D-like rules it is no surprise then this illusionist cleaves very close to the source material.
I stand by my assessment of this book that I made then. This is hands down one of the best books of this type you can get and really captures what the OSR is about. Also, if you are playing an illusionist of any sort in any of the games I have mentioned, then by all means get this book.