Database administration site on Drupal: entities vs. manual programming I've been asked to build a small database administration site based on Drupal. The site should have basic editing possibilities of the existing database with several tables. (The structure is not complicated). 

To get it more clear, one table contains books being sold in the publishing center. The book has a set of identification numbers, title, e.g. The structure of book is very similar to basic node with fields.

The question is: Is it a good idea creating a custom entity with described architecture and process data in terms of 'book'  entity (and therefore the database will be automatically modified according to current architecture) OR it's better to implement simply some interface and update database manually using db_query etc. ?
While I can't see any significant benefits to doing this with Drupal, I think this should generally work. I've converted old systems that were using db_query and custom code to Drupal 7 Entities with the Entity API module with success, and I've been pretty pleased with the results. As long as the schema is solid, without issues, or you can modify it as needed, this will work fine.

Depending on the data structures and the normalization of related entities/properties you may need to create your own EntityController to override the loading (and saving if using Entity API module) to ensure that the data is queried and updated properly.