I adore this book! There's seriously nothing I can say that I do not like about it, and so this review may just come off as a very biased one. It's just one of those stories, filled with colorful characters and eloquent writing, that makes me feel... simply put... happy! It gives me that feeling like I just spent the entire day lounging around in a cute summer dress, on a wide open field, on a glorious Summer day. It's as lovely as a Jane Austen novel, and reminds me a bit of Jane Eyre as well.
So if you are a lover of the Classics, read this. Read it for the characters that you would want to get to know in real life, for their development, for the plot, or maybe for the beautiful, descriptive passages and quotes. Read it to remind yourself why you like reading in the first place.
Don't read it if you are not a fan of the Classics. If you just were never into the usual pace or the usual tone the genre sets on most of the time. But try it nonetheless; because I think whether you like I Capture the Castle or not, you'd still appreciate it in one way or another.