Formal:
* Engrossing: This implies that something completely captures your attention.
* Captivating: This suggests a strong attraction or allure.
* Intriguing: This implies a sense of mystery or curiosity.
* Stimulating: This suggests that something is mentally or intellectually engaging.
* Riveting: This emphasizes that something is intensely interesting and holds your attention.
Informal:
* Cool: This suggests something is interesting or impressive.
* Awesome: This implies something is amazing or wonderful.
* Mind-blowing: This indicates something is extremely impressive or surprising.
* Amazing: This conveys a sense of wonder or awe.
* Fabulous: This is a more general term for something that is excellent or impressive.
Other options:
* Absorbing: This implies that something is so interesting that you are completely drawn in.
* Alluring: This suggests that something is attractive or tempting.
* Enthralling: This implies that something is captivating and holds your attention.
* Mesmerizing: This suggests that something is so fascinating that it hypnotizes you.
* Remarkable: This implies that something is noteworthy or extraordinary.
The best word to use will depend on the specific situation and what you are trying to convey.