Is there a systematic theology resource based solely on the words of Jesus?

Numerous Bibles have a "The Words of Christ in Red Letter" feature. Understandably, there is some debate concerning which verses and words should be in red (but this question is not about that.) This question is: What is a good resource on systematic theology that _only_ looks at the verses in red -- i.e., instead of being based on the entire Bible, is based only upon the words that Christ says?