時をかける少女 is pretty easy as far as books go. 魔女の宅急便 was maybe a bit harder, but there was also over half a year’s difference in my abilities between the two, so it’s hard to say how much of the difference is from that.
Also just to chime in in general. I agree with @marcusp that it may not be worth a complicated nomination process for something like this. I thought @marcusp did a great job by just picking something simple and cute and saying “hey I’m reading this, who wants to join”. Just my two cents.