Vernon's Annotated Constitution of the State of Texas
This set of books is, without question, the most detailed and up-to-date resource available to research the Texas Constitution of 1876.
As reflected on the current publisher's website, the first seven books (Volumes 1, 1A, 1B, 1C, 2, 2A, & 2B) were published in 2007. The last book in the set (Volume 3) was published in 1993. However, the entire set is updated annually with so-called "pocket parts."
The preface to Volume 1 provides a good overview of the substantive content of the eight-volume set.
For example, the preface describes the included "Notes of Decisions" in the following terms: "This feature, the distinguishing hallmark of Vernon's Texas Codes and Statutes Annotated, consists of a thorough treatment of judicial constructions of the Constitution, by both the federal and state courts, as well as opinions by the attorney general. Annotations referring to judicial constructions and attorney general opinions relevant to each section are grouped under descriptive headings or catchlines. These catchlines are numbered and alphabetically indexed for greater certainty and convenience in research."