Any good (and inexpensive) books on RNA/DNA? I’m a retired physicist but dismally ignorant of organic chemistry. Maybe there are some old editions of textbooks …
I’m a retired physicist too. 
There isn’t really a great up-to-date book on RNA/DNA biology and structure-- if you write one, there would certainly be a market. An older textbook written by the field’s pioneers with the basic facts is by bloomfield, tinoco, crothers (you can find it for free in google books).