If you plan to work in aerospace: Yes. If you are a hobbyist: Yes, used. If you are just curious: Borrow it from a library, but be prepared to buy your own copy after Chapter 3.
If you’ve ever asked, “How do I actually design a rocket engine?” there is one answer that professors, NASA veterans, and SpaceX engineers will unanimously give: rocket propulsion elements 10th edition
Use this book for the physics (which never changes), and supplement it with recent AIAA papers on 3D-printed copper alloys for combustion chambers. The 10th edition tells you why copper is good; the internet tells you how to print it. Final Verdict Rocket Propulsion Elements, 10th Edition is not a coffee table book. It is a reference you will dog-ear, spill coffee on, and tab with sticky notes. It doesn't teach you "rocket science" as a metaphor—it teaches you the actual engineering required to push mass off a planet. If you plan to work in aerospace: Yes