I personally sold cloth and leather BODs (and all leathers from regular to barbed, at that) for the better rewards (that fit the large BODs for CBD, spined and horned) for 3000 each, and most of the time they didn't sell until it was time for the artisan festivals. And, I'm on a shard that's always been crafter-heavy.
So, for the tailor BODs, probably 1000 per BOD at most. About the same for smith and tinker weapons BODs. Someone else can probably give better advice on colored metal armor BODs. Most everything else has ingredient costs that are so mixed up compared to the reward
As for other concerns....
1. Even with a buyer, it would probably be best to sell them using a vendor as a go-between. A vendor can only hold as much as a player, after all. You can put the books 1-2 at a time on the vendor, and have the buyer buy them, go to drop them off (or switch characters, if holding them in their banks for later cross-sharding).
2. Try to keep books under 300 BODs each - preferably under 250 BODS, for selling. Remember that BOD books have an item count as follows: 1 for the book and first 4 BODs, +1 for every 5 (or fraction of 5) above. A typical buyer will probably have 5-15 items in their pack, so will only have room for 110-120 items.
A full book 500 BODs counts as 101 items. Backing it down to 499 makes it only 100 items. A book of 499 only leaves room for another book of 124 BODs in the remaining space of a pack animal.
A book of 249 BODs counts as 50 items.
A book of 299 BODs counts as 60 items.
A book of 309 BODs counts as 62 items, and is the limit you would want to go to, if you know that the buyer is putting the books into a pack animal (2 such books will be 124/125 items in a pack animal).
But, you can't take it for granted that any given buyer (or even you, when doing the sale), will have the room in your pack for 2+ books totaling 500 BODs or more.
So, the most smooth transactions would be 2 books of 309 items or less each, priced each as a sale of the whole book in a vendor. The buyer buys them, and as they buy and put them somewhere for transport, you replace the bought books. Safer for you, safer for the buyer. Plus, it allows you to take as long as needed to make the transactions, as you don't have to be there for the sale - just try to load the vendor as close as possible to the buyer's arrival, and remove the books if they back out of the sale or get held up and are running late.
Added: If you're willing to take the commission hit and have the free room in the house, a commission vendor is great for it (you could possibly raise the asking price by the commission price).
If you know and trust your customer (unlikely since you're talking about selling them here), you could theoretically have pack animals friended so that you could move books into their pack animals, or buy 5 packies and transfer them to the buyer with the books. Still, this means you'd have to sort books (and probably BODS between books) to get them to where you maximize the fit into the packies (2 62-count books, etc.)