A major weakness of many guitarists (new and experienced) is their inability to read written music, in particular rhythm. While most students cannot avoid having to grapple with reading the pitch (in the absence of TAB), many use their ears to avoid having to read the rhythm. This is due in some part to the large range of method books and sheet music that come with CDs.
I have found that this weakness can be overcome reasonably quickly in older or more experienced students through the use of sequenced rhythm exercises (no pitch). These allow the student to focus on the rhythm without the worry about where to find the note on the guitar. I primarily use two books for this purpose. Modern Reading Text in 4/4 and Odd Time Reading Text by Bellson & Breines.
At the most basic level, the exercises from this book can be clapped or played with a single note on guitar. This would be accompanied often with a metronome and/or the student counting the rhythm as they play. As students become more familiar with a rhythmic concept I may expand the exercise to include a set melody or chord progression, allowing the student to test their mastery of the material. I also use the materials in the books purely as improvisation exercises as they force the player to adapt their material (scales, arpeggios, melodic cells, etc.) to fit the given rhythm.
These texts are not great for guitarists looking to teach themselves how to read rhythm. They may be used by players who have basic reading skills (minims, crotchets, quavers and semiquavers in both notes and rests) and are looking to develop these skills with a carefully arranged series of exercises, slowly building in difficulty. The books are quite dry so make sure you take a look inside the book before you buy. I understand that there are a number of newer books on the market of a similar nature and I will let you know what I think when I have a chance to check them out.

