Sorry not sure why I've replied to previous post...agree with essential oil roller
Handy for all sorts of things.
Wind settlers....tmi maybe but often get gassy on flights, water bottle, eye mask, really good moisturiser, lip balm, small packets of pretzels or snack type things, packet of shortbread, tissues, small pot of vicks, mirror, £ coin or.2..... some uk airports you have to pay for trolley (LGW!!), hand sanitizer, sanitising wet wipes, face wipes, paracetamol, boiled sweets, mints, mini mouthwash, eye drops. Tea bags if they like a particular type of tea... I've taken peppermint with me before.
These are generally the things I have with me when I fly. Remember there is still the 100 mls liquid rule in place so be careful with toiletries.
A lot will also depend on whether it's enconomy or Business.
I personally don't bother with pure books etc and when I take books I barely read them. I will load up on audible though.