not very polite, no. but yes I agree, you aren't likely to get them for free - they're not the kind of thing that is "big for me but peanuts for someone richer", as a lot of things are in Mabinogi, the higher-level Bard skill books are hard for anyone. Also, many of them aren't tradeable at all, like Nele's wretched Composing Rank D book, which I'm currently trying to summon up the willpower to get myself! So you'll definitely just have to grit your teeth for those...
When you get to the stage of needing Empty Bottles (Musical Knowledge rank something or other) though, you can normally borrow those if you ask around, as they can be reused as often as you like.
Musical Knowledge F to C and Composing F to E, C to A and 5 to 3 you can just buy from NPCs, though they get expensive at higher ranks (the last Composing books require Ducats, by the sackful). Where are you up to so far?