About this time of year, many newspapers and magazines publish list of books to read while on holiday. Some mention classics, some include recently published rather heavyweight non-fiction, most include fairly lightweight fiction. Many assume that the holiday is flying off somewhere, lying on a beach for a couple of weeks, perhaps doing a little bit of exploring in the local area, and doing a fair bit of drinking and dining out. But holidays and people who take them are much more varied than that, and may include hiking or rambling in a variety of European mountainous areas, deep-sea diving, sailing, paragliding off a mountain somewhere and other adventurous pursuits. Or possibly staying in a rented house or gite, in the middle of some quiet countryside, with or without a pool. Or even cruising, if that's what grabs you (not me, I suffer from sea-sickness).
I think that the type of holiday will surely influence to some degree what you take to read, even if it's all loaded on to an e-reader. If you're doing a lot of activity during the day, and going out in the evening, finding the time to concentrate on a more demanding read may be difficult, so something shorter and lighter may be easier to pick up and put down, while staying put in one place may make the choice of something more demanding just the job. What every constant reader probably wants is a choice of reading matter, to suit their mood and the circumstances they find themselves in, and now that is much easier to organise on an e-reader than taking a pile of books, despite my own preference for the book as a physical object.