You can use any topcoat over an oil based primer, but there is really no reason to use oil paint inside on walls. I would use a flat latex unless it's a low kitchen or bathroom where you would want some washability and moisture resistance then you would use a satin or eggshell or even a washable flat.

Definitely wait a few weeks before shelving your books to give the paint time to cure. It hardens as it cures. If you put books on the shelves too soon, they will mar the paint and could stick to it a bit, too. I would go with a semi-gloss. Benjamin Moore is a good brand. You could also look into CabinetCoat, which is an acrylic resin paint, I think---more durable than latex but still water based. I used it on trim in our house and was very pleased with the results. It's more self-leveling than latex and brushmarks just settle out. It does tend to form drips and sags more than other types of paint AND it dries quickly so you need to be vigilant about checking your work as you go. Here is a link that might be useful: CabinetCoat paint

Thank you. I sanded too hard after applying the poly so needed to refinish. Sanded down, and used a gel stain this time and a two coats of poly over it. Turned out better I think!

House is 25 yrs old, guessing existing paint is 15yrs old. For short periods of the year, the shower is used daily, with fan, but as part of this renovation, we discovered that the exhaust fan did not vent to the outdoors, only to the attic. So probably more moisture than there would be ideally. (So we also are installing new properly vented fans.) Didn't clean walls with any product, wiped down. I spoke to Valspar this morning. They suggested I should have cleaned and lightly sanded walls, spot primed the mud. Regarding my concern over peeling, the rep said the paint can take up to 30 days to cure and that he would expect it to harden and adhere more during that time. Then to spot sand lightly where needed to repaint peels. I see now that I can't just go by what the paint label says, but the problem still remains - What's going to happen with this paint that is now on the walls? I have more painting to do, so I'll wash and sand the remaining walls. I can't put my whole project on hold for 4 weeks to see if this paint will stop wanting to peel, but I really don't want to have to strip it all.