Love is not convenient.
For all the words that poets have spilled trying to describe love over the years, it seems to me that it is easier to describe by explaining what love is not. Love is rarely on your schedule. It would be amazing if we could simply snap our fingers and have love whenever we want it, but if that were the case, it wouldn't be love. The pain that is a huge part of the experience is one of the reasons it matters. Love is not easy. Love is not casual. Love is not interested in what we want.
"The Fault In Our Stars" is a very simple story about two kids, each struggling with cancer, who find each other at the least convenient time and fall in love. I don't think any part of that sentence is a spoiler. It's just a description. The details are what matters, and the script by Scott Neustadter & Michael H. Weber, adapted from the well-loved novel by John Green, is very smart and fairly unsentimental, which works to the material's advantage. When you're talking about a movie that deals with two young people with cancer falling in love, the potential for that to be hugely sappy is overwhelming. I haven't read the book, but the film nimbly avoids most of the things I expected from it, and does so in a lovely, thoughtful way.