While the two words may have similar meanings, there is one key difference: Bibliomania describes the intention to create a book collection, tsundoku describes the intention to read books and their eventual, accidental collection.
I used to fret over my increasing inability to achieve “bookshelf zero”, but I’m slowly resigning myself to the fact that having forty to fifty books in the “want to read” column is just becoming my new baseline, given my constant exposure to temptation. A friend recently said she prefers having unread books lying around because of the potential they represent. Likewise, I’d rather maintain the feeling of childlike excitement in finding a new book I want to read, even if it keeps me chained to my Sisyphean task.