If you thought textual criticism of the NT was difficult, then the subject of OT textual criticism will thoroughly frighten you. JTA reports on the difficulties inherent in this subject in its recent article on the labours behind "The Hebrew Bible: A Critical Edition". The difficulties are not trivial:
"Some of the errors are natural outgrowths of the process of scribal transmission — essentially typos in which the scribe mistook one letter for another, skipped a word or transposed words. In other cases the scribes may have changed the text intentionally to make it more comprehensible or pious.
"The level of variation differs from book to book. [General editor of HBCE Ronald] Hendel estimates that it ranges from approximately 5 percent in Genesis to some 20%-30% in books such as Samuel and Jeremiah. While many changes are small, others are more substantial.
"Just before Cain slays Abel, the Masoretic text announces that Cain speaks but offers no dialogue. Both the Samaritan Pentateuch and the ancient Greek translation called the Septuagint supply the missing speech: “Let us go out to the field.” In this instance, emending the text is relatively straightforward.
"But elsewhere the task becomes complicated. The book of Jeremiah in the Septuagint is approximately 15%-20% shorter than the version in the Masoretic text, and the text appears in a different order. In this case, editors are not just dealing with glitches but with entirely different versions of the same text."
The first volume - Proverbs - is due to be published this (northern) autumn by the Society of Biblical Literature. Full article is here: http://tinyurl.com/pbv4kkj