I would structure the book by task, showing how different languages would implement the same task. For example, using a marc parsing library in java, groovy, python, ruby, perl, c/c++/objective c, Haskell. Implementing same. Using a rest API Implementing a rest API Doing statistical analysis of catalog records, circulation data , etc. Doing knowledge based analysis of same -- Treatment of each topic and language is likely to be cursory at best, and I am not sure who the audience would be. A series of "<language> for librarians" books would seem more useful and easier to produce. Simon