That's only a problem when you move a lot. Like I have (5 times in 8 years.) But then I can literally say, I have a Ton of books 
No, when you stay in one place for too long it become a problem too. When you have put in all the book cases that really make sense, and the books start piling up on tables and floors anyway....

(if you love books, and marry someone who loves books even more, you may or may not have children, but you will certainly have many, many, books to love .... )
On the general dead trees vs PDF issue -- personally for things with full page layout structure (like an illustration of a Barghest at the top of the page, with text and stats below, frex), I much prefer physical books. I'm generally reading game pdfs on a laptop, where you can't see the whole page and have readable print at the same time, so you really lose the impact of the layout (I may not even loathe Street Grimoire so much if I'd bought the physical copy rather than the PDF, but hard to be certain). On the other hand, something with many little bits of info that you might want to find quickly, PDF for the searchability.