Set up a wither skele drop to 1 hp pit, picked up sword of the xzepher. 15 sec or so of swining = 30 levels. Enchant book. Repeat. I actually built the thing to get skulls, but a few minutes of looting zepher made the need for automation vanish.
Early on, level 1 book enchants were nice for getting unreaking/protections/sharpness/e.t.c 1 books to get tools up to level II.
I'll eventualy grind for a unbreaking III book if I havn't found one in a loot chest to put on a repair/eff V Tool or sharpness/repair sword So that they cause less flux repairing ^^'
If flux / durability is an issue you could always try for a nanosaber...it won't have the AoE aspect of the zephyr, but you can (last I checked) throw book enchants on it to make it more effective and it's only a few more hits...get one with disjunction IV and you might just be able to 1 shot a wither skel or enderman
If you want to have some fun with it you could always try Xeno's Reliquary... Holy Hand Grenade (not of Antioch) should be able to kill off all those skellies without damaging the surrounding area at all (only damages entities). Maybe even holy water or w/e, dunno if it's a splash potion but if it is then that could also be interesting...