I am using a somewhat obscure mathematical technique in one of my papers, and there is only one reference text (so far as I am aware) that collects all the important examples of the technique that I need. However, I am leery of pointing my readers to this book without a warning, because the reference book has numerous problems.
The book was clearly compiled from a number of earlier sources, including the original research literature. These were put together without much care. Notation for the various functions involved changes from one table to the next. (The same object may be referred to an upper case U, lower case u, or a cursive letter.) Even more seriously, there are many misprints, some of which are more obvious than others.
I feel like when I reference this text, I should put some caveat lector—something like, "Details about the transformation and all the important examples that will be needed in this paper may be found in ; however, the reader should be advised that  contains multiple typographical errors." But that sounds somehow unprofessional to me.
Is that kind of statement unprofessional sounding? If so, how can I convey the information that this is a poor quality source—it just unfortunately happens to be the only comprehensive source in existence.