Development:
Two books by Uncle Bob, ‘Clean Code’ is on coding techniques, where ‘The Clean Coder’ is about professionalism and soft skills. Both are excellent books.
Relational Database Theory:
Relational Theory for Computer Professionals
A great introduction to the relational model, relational operators and database design. CJ Date has a lot of books available on this topic, but this one would be a good starting point.
SQL Server:
The ‘Deep Dives’ are collections of writings by MVPs and other notable people in the SQL Server community, covering Admin, Development, BI and other database topics.
SQL Server – Design:
Database Design for Mere Mortals
A good guide to the basics of normalization and database design.
SQL Antipatterns: Avoiding the Pitfalls of Database Programming
It’s as important to know what not to do as it is to know the correct techniques.
SQL Server – Internals:
Pro SQL Server Internals: A very comprehensive look at SQL Server internals and architecture.
SQL Server 2012 Internals & Troubleshooting
The first chapter is the best overview of SQL Server Architecture that I’ve read.
SQL Server – Security:
Securing SQL Server
Denny Cherry covers a wide range of topics, from database encryption options to auditing to granting rights to database objects.
SQL Server – T-SQL:
Anything by Itzik Ben-Gan, but in particular:
Microsoft SQL Server 2012: T-SQL Fundamentals
NoSQL:
Seven Databases In Seven Weeks
A good introduction to PostgreSQL, Riak, HBase, MongoDB, CouchDB, Neo4J and Redis.
NoSQL Distilled
A good introduction to the varied types of NoSQL database systems.
SQL Rob 