Spellbinding describes something so interesting that you cannot look away or stop listening — a film, a story, a performance, a speaker, sometimes a view. The picture inside the word is magic: a spell has been cast on you and you are tied in place by it. That image tells you how strong the word is. It is not "quite interesting" or even "very interesting"; it means your attention was completely taken, and you probably forgot the time. Because it is that strong, using it for something ordinary sounds silly — a spellbinding textbook, a spellbinding meeting. Save it. It describes the thing that holds you, never the person held: the concert was spellbinding, and you were spellbound. Keep those two apart and you will use both correctly. In tone it leans literary and is a favourite of reviewers — you meet it in film reviews, book covers and concert write-ups far more than in conversation. Two friends of a similar strength are gripping (more about tension, wanting to know what happens next) and mesmerising (more about beauty or a hypnotic quality). Though actually, from all that reviewing use the word has worn a little thin: when every poster says "spellbinding", readers start to hear "the publisher liked it". In your own writing that means it works best when the thing really did stop you dead, and best of all with one concrete detail beside it, so the reader believes you.