The Leavitt reading studies books certainly warrant a look. I have worked with Melodic Rhythms for Guitar and it is great for the right hand and learning to quickly recognize particular rhythms - if you accept the basic premise of always picking down on the downbeat, and up on the upbeat.
I also have a copy of the Reading Studies for Guitar (Positions One Through Seven). The treatment in this book is extensive and I'm sure it would be helpful to work through, but I've never been able to stick with it for long. I prefer to read through music written for other instruments, and work out my own fingerings and positions.
Leavitt's "reading studies" books tie in somewhat with his three book series A Modern Method for Guitar which is the most extensive academic treatment of pick-style guitar I've seen. Leavitt has a specific set of fingerings and a specific approach to picking (as mentioned earlier), so there's a certain amount of "buy in" implied to work with this material. So far as I can tell, all his material is meant to develop technique and reading ability, but is not always particularly inspiring.
Another interesting book is The Fingerboard Workbook "Concepts in logical fingering" by Barry Galbraith. I found the fingering concepts useful, but never really tackled the studies. Check out the other books in this six book series for other possible technical material (Daily Exercises in the Melodic Minor and Harmonic Minor might be a candidate).
You can also definitely use books meant for other instruments when studying the guitar. Any material you find interesting and helpful is worth consideration. You don't have to limit yourself to guitar-specific material.