Propulsion
Rocket Propulsion Elements by George Sutton
One of the best general introductions to rocket propulsion. Has chapters on nozzle flow, liquid propulsion, solid propulsion, and hybrids.
Liquid Engines
Modern Engineering for Design of Liquid Propellant Rocket Engines by Dieter Huzel and David Huang
A "how-to" guide for designing liquid propellant rocket engines. You should probably read RPE first to get a broader idea for the field. Compared to RPE, Huzel and Huang is more applied; the target audience of RPE seems to be a university student asking "how does this work" while the target audience of H&H is a junior engineer asking "how do I build this"?
Usually referred to as "Huzel and Huang" because the title is too long.
An earlier version of the text, NASA SP-125, is available on the NASA Technical Reports Server.
Ignition! An Informal History of Liquid Rocket Propellants by John D Clark
Ignition is a narrative story, not a textbook. It describes the merits and development of liquid propellants.
Nowadays, it seems that everyone and their grandmother knows that LOX/RP-1 is the best propellant combo for cheap space boosters, and N2O4/UDMH is the way to go for storable propellants. But how did we figure this out? At the beginning of liquid rocketry, back in the 1950s, there was a wonderful, magical period; a time before OSHA cared if you blew yourself up; a time before the EPA cared if you blasted hundreds of pounds a second of mercury into the atmosphere; a time when one could casually order a tanker truck full of liquid fluorine; generally a time before anyone knew what the fuck they were doing. In this milieu, a cadre of chemists and engineers tried burning pretty much every chemical they could get their hands on in a quest for more performant propellants. Ignition tells their story.
Solid Motors
Propellants and Explosives: Thermochemical Aspects of Combustion by Naminosuke Kubota
Describes the chemistry and combustion process of many solid propellant formulas. Also includes a brief overview of nozzle flow and thrust generation.
High Power Rocketry
Modern High Power Rocketry 2 by Mark Canepa
Brings the reader through Level 1, 2, and 3 of HPR. Chock-full of information and pictures about building rockets at the HPR scale.
Topics in Advanced Model Rocketry
Materials
MMPDS Metallic Material Properties Development and Standardization by Battelle Institute and the FAA
Gives material properties for many aerospace alloys.
MMPDS is the successor to MIL-HDBK-5H Metallic Materials and Elements for Aerospace Vehicle Structures by US Department of Defense.
Recovery
Parachute Recovery Systems Design Manual, by T.W. Knacke
Discuss various forms of recovery systems. Mostly applicable to large-scale launch vehicles (L3 and larger) and spacecraft.
Structures
Composite Airframe Structures, by Michael Niu
Discusses the engineering of composite airframes, mostly relating to airplanes but relevant to rockets. Covers materials, manufacturing, joints, safety and testing.
Shigley's Mechanical Engineering Design, by Richard Budynas
Focuses on the engineering of reliable systems. Covers all sorts of engineering concepts, but the most useful for us is Chapter 8 which covers fasteners.
Composites Manufacturing, by A. Brent Strong
Focuses on the manufacturing of all kinds of composites. There's all sorts of cool stuff about various chemistries, and processes, and even ceramic composites.
Mechanism Design
FUNdaMENTALS by Alexander Slocum
PDF Provides an overview of the basic principles of and physics behind design with real world applications.