Learn Spanish (Spain): Me encantó esta novela, que leí en verano. - I loved this novel, which I read in the summer.

While we often use the imperfect to describe ongoing feelings in the past, the preterite (encantó) is used here to sum up your overall reaction to a completed experience. You finished reading the book, and your final verdict is that it enchanted you.

Since I am the one loving the novel, why isn't there a personal "a" before esta novela?

Verbs like encantar and gustar work backwards compared to English. The novel is actually the subject of the sentence (it is enchanting to you), and you are the indirect object (me). Since esta novela is the subject, it never takes the personal "a".

Could I use la cual instead of que after the comma?

Yes. Because the comma makes this a non-defining relative clause (adding extra information rather than specifying which novel), la cual is grammatically correct. However, que is much more natural and common in everyday Spanish, whereas la cual sounds quite formal or literary.

The English translation says "in the summer", so why is there no definite article before verano?

When using the preposition en with seasons, Spanish speakers frequently drop the definite article (el). Both en verano and en el verano are perfectly correct, but en verano is highly idiomatic and common when referring to the season generally.