None of the books which I read made any sense.
Nyanatiloka in his Buddhist Dictionary in the
entry on Khandha says:
"Some writers on Buddhism who have not understood
that the five khandha are just classificatory
groupings, have conceived them as compact entities
( heaps, bundles ), while actually, as stated above,
the groups never exist as such." page 98
If it is just a fivefold classification framework, then
there is really nothing to understand.
The real mystery is what is being classified into these
five groups, or what is a dhamma.