I'm having trouble reconciling Feynman and Adleman's advice. Adelman would rather read a novel than work on anything but the most important problems whose time has come. Feynman got his mojo back by understanding spinning plates, and famously loved to goof around with physics problems. Hamming would probably agree with Adleman here.
Perhaps they would agree that one should have some ambition and do what's important, but Feynman would have you sneak up on it from behind, while keeping the juices flowing with playfulness. I'll go with that.
Well, there's no reason to reconcile them. They can have differing opinions on how to approach problems. But don't think that Feynman was working nonstop on spinning plates and those diagrams he invented. He liked working in strip clubs, started drawing a bunch, and randomly learned Portuguese when he followed a pretty woman onto a plan to Brazil. There he joined a street band and learned to play instruments while continuing his drawing. This seems pretty comparable to the idea of reading a book for a break.
Regardless, you can find people's ways of focusing to differ and not have to reconcile every smart person's personal way to study and research.
To me, Feynman's example of the plates is something that you do in addition to Adleman/Hamming's advice.
Of all the problems to work on, work on those that have have a reasonable angle of attack (Adleman/Hamming), that you have the ability to solve (Feynman). And in addition, make sure you plant little seeds instead of just working on big problems after you've succeeded (Hamming in 'You and your research'), which amounts to being able to play with spinning plate problems (Feynman)
Perhaps they would agree that one should have some ambition and do what's important, but Feynman would have you sneak up on it from behind, while keeping the juices flowing with playfulness. I'll go with that.