Use a bookplate to label your books. Generally, bookplates devalue collectable books significantly, but, In my opinion, not nearly so much as direct writing in the book. Design your own bookplate, or hire a graphic artist to design it, and get it printed by a competent printer. In fact, with the availability of laser printers and the good graphics programs, you can probably custom design your own bookplate and print it. Acid free paper is not hard to come by now days.
Bookplates are the trAdditional and proper way to identify one's books.
Take your time. Look at other bookplates and get an idea of what's been done. In this, there is nothing so banal as repetition of the same tired images and motifs. Buy shelves big enough so that your books will stand up and clear the shelf above. Get shelving deep enough so you have some space behind the books.