KU is definitely hit or miss. I get most books from my excellent public library system, but ku will surprise you with gems in military history and sci fi, sometimes with audible narration included. Sometimes I’ll take a chance on an author or genre I don’t normally look at - I read Mr. Polfus’ books on ku and wouldn’t have read them otherwise, for example.
ku isn’t essential, but nice to have. The library, now that’s essential.