Indeed. As a young voracious reader I used to think that more reading is an unmitigated good until I came across Schopenhauer and his aphorisms. I try now to be more selective, life is short, and to engage more deeply with what I read.
"The art of not reading is a very important one. It consists in not taking an interest in whatever may be engaging the attention of the general public at any particular time. When some political or ecclesiastical pamphlet, or novel, or poem is making a great commotion, you should remember that he who writes for fools always finds a large public. A precondition for reading good books is not reading bad ones: for life is short."
“Reading is merely a surrogate for thinking for yourself; it means letting someone else direct your thoughts. Many books, moreover, serve merely to show how many ways there are of being wrong, and how far astray you yourself would go if you followed their guidance. You should read only when your own thoughts dry up, which will of course happen frequently enough even to the best heads; but to banish your own thoughts so as to take up a book is a sin against the holy ghost; it is like deserting untrammeled nature to look at a herbarium or engravings of landscapes.”
Nowadays the analogy to “not reading bad books” is “not consuming social media”. Reading a bad book seems so much more beneficial to your concentration, focus and attention span than doomscrolling that it’s a valid recommendation. The bar is low.
I can see his point that it is worth learning to think for yourself, but if you then try to publish your thoughts without understanding what else is out there (e.g. by reading about it), the results could be very embarrassing. This would seem to apply in both philosophy (which I'm assuming Schopenhauer was discussing) and (say) genre fiction.
Incidentally, having quickly scanned some of Schopenhauer's actual writing [0], I found statements such as "women are suited to being nurses and teachers of our earliest childhood precisely because they themselves are childish, silly and short-sighted" and women "are inferior to men in respect of justice, honesty and conscientiousness". If I'd come across these first I'd be very reluctant, rightly or wrongly, to uncritically accept his views on other subjects.
[0] https://www.scribd.com/document/509571816/Schopenhauer-Arthu...