In my opinion, it is essential to have spacetime diagrams and use them throughout, emphasizing the geometry of spacetime... and encouraging the use of appropriate analogies with Euclidean space.
"A spacetime diagram is worth a thousand words"
(Maybe "spacetime diagram" is too scary...
just say "position-vs-time graph".)
Maybe introductory relativity problems are essentially hyperbolic-trigonometry problems involving a Minkowski-right-triangle, where a length or an "angle" (rapidity) must be found. One has to reformulate the word problem into a spacetime diagram.
Many books have good presentations of formulas and formalism, but not enough connection to the spacetime geometry.
Books that I like that emphasize the spacetime diagrams and "spacetime thinking"... in order of increasing difficulty...
- Bondi, Relativity and Common Sense (especially the development of "operational definitions via the radar method" and the $k$-calculus [secretly the eigenbasis of the Lorentz boost]. ( https://en.wikipedia.org/wiki/Bondi_k-calculus https://www.physicsforums.com/insights/relativity-using-bondi-k-calculus/ )
- Geroch, General Relativity from A to B (although it may seem verbose, it is unusually deep in terms of spacetime thinking)... I read it as a first-year undergrad (assigned as optional reading)... interesting but I didn't appreciate until I sat in on a more advanced course by Geroch (see reference later). Even in the advanced course, he made similar points at a more advanced level. He is a remarkably deep thinker.
The emphasis on spacetime thinking, operational methods, causal structure, modeling spacetime structure.
#cut for length#