Notably some of the books are much rarer than others. Any given book is worth 20 candy so it's worth the stick it takes to clear it if you finish the questline. But full sets will depend on you finding those rare books. I find lots of common ones, but only a couple of the silver ones, and none of the gold one between several worlds that were hunting for wishing wells. For point of comparison with graviton's experience above, most of these worlds are not super-far along in the questlines ; they generally only had 1 set of tools purchased to work with.
At any rate mostly the strategy if you're not going for specials in order to maximize your progress towards asylums would be to use your tools wisely (i.e. find good scenarios for using brooms and cauldrons where they reveal many dark cobwebs or collect multiple items saving you sticks; don't spend a bunch of tools just to reveal a single dark cobweb that's a dead end), and to treat pumpkins (almost) as though they were empty tiles in your decisions as to what you clear or don't. You can't find more books by simply willing them to show up so there'd be little more you can do than avoid things that don't help you along in your goal to get more grand prizes.
I haven't made any effort to run the numbers on how many asylums upgrades you're likely to gain but i doubt 2 fully upgraded is in reach without (many) diamonds. And so much of the asylum's value is in the final upgrade that there's little point in chasing extra upgrades unless you're going for a full one.
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