The majority of books related to Development Studies in the Angus L. Macdonald Library are located in the broad HA - JZ sections (3rd floor). However, the Marie Michael Library at the Coady Institute also has a large collection predominantly devoted to Development Studies. These will also show up when you search in the Library catalogue, but will have Dewey Decimal call numbers (they will start with numbers rather than letters).
You may find that browsing the shelves is as useful as searching in the catalogue! Just do a quick search in the catalogue, write down the call numbers for a few relevant books, then head to those areas to browse for books in those areas.
The following eBook collections have a fair amount of Development Studies content, and can be accessed both on and off campus: