Ehrman's book mixes fact with a great deal of speculation. I would not recommend it as a starting place.
For a more factual treatment, I'd recommend starting with the wikipedia article on "textual criticism" (the process of reconstructing documents from imperfect copies). Its section on the New Testament has a list of the major textual problems, most of which have their own wikipedia articles.
If you want to get into books, David Alan Black wrote a fairly nice introduction to New Testament textual criticism. Bruce Metzger and Kurt Aland's books are both pretty widely respected as well. If you want to see the changes passage-by-passage during study, consider using the NET Bible (net.bible.org) and watching for notes marked "tc".
I wrote a commentary on a commentary of that. Getting meta, I know. :) But I think it's valid to consider both sides because Ehrman seems a bit misinformed about some things.
For a more factual treatment, I'd recommend starting with the wikipedia article on "textual criticism" (the process of reconstructing documents from imperfect copies). Its section on the New Testament has a list of the major textual problems, most of which have their own wikipedia articles.
If you want to get into books, David Alan Black wrote a fairly nice introduction to New Testament textual criticism. Bruce Metzger and Kurt Aland's books are both pretty widely respected as well. If you want to see the changes passage-by-passage during study, consider using the NET Bible (net.bible.org) and watching for notes marked "tc".