I would like to read a lot of the newer Voyager books, which the library doesn't have, but I'm not willing to pay what they cost at this point. I know I'm missing some interesting stuff, like the last Borg invasion that keeps getting mentioned and why they aren't around anymore, or why a Trill counselor is in command of a starship (Seriously, Ezri gets a ship? Who gets one next, Bashir? Nog? Are they just handing them out now?) but paying more than $1-2 for a book just isn't something I like doing unless I absolutely have to.
If you want to read a book, can you request the library orders it? That would enable you to read e.g. VOY without paying more than $2. There's also always Kindle - no shipping costs, no shelves filled to the brim with murdered trees.
Concerning Ezri, Bashir, Nog and Co.: Ezri moved to command track and earned her ship. Bashir is a Commander and technically only one pip away from command, though I think he would have to serve as executive officer first. With everyone except people on the Enterprise
in the 70s) receiving promotions more or less regularly, it is only a question of time until everyone ends up as captain. Unless, of course, they desert Starfleet or die.