Hi Ken,
I think an deep understanding of the mathematics involved is essential- there are some popular books which give overviews of GR and particle physics but without understanding topics like differential geometry, exterior calculus, group theory and Lagrangian dynamics it’s almost impossible to accurately convey the subjects properly. It’s rather like learning a foreign language by repeating constructed sentences but not knowing the meaning of the words.
I’ve been teaching our General Relativity course at Leicester University which our 4th year MPhys students can opt to take and I would recommend:
-‘Introducing Einstein’s Relativity’ by Ray D’Inverno
-‘A short course in general relativity’ by Foster and Nightingale.
Not convinced about a variable Planck’s constant for a variety of theoretical and experimental reasons at the moment.
Cheers,
-Paul