"A few books"
yes, for adjectives and quantifiers like थोड़ी, the singular and plural feminine forms are the same, थोड़ी किताब or थोड़ी किताबें
Oh, of course, thank you. I'm afraid I came back to this after a bit of a break.
"a few" English can mean both "some" (ie. koi) and "not very many" (thori); in English, the more natural version of "not very many" is really "few" more than "a few"