Definitely don’t need answer fast. What word would you use for an academic class which requires a lot of studying but you never find frustrating? Perhaps there’s a lot of attention to detail required or there’s a lot of reading and you need to constantly look up references. But, you never once are close to the point where you want to throw the book across the room and scream, ‘I’ll never understand this!!’
“Fun”?
Fast paced and enjoyable? Four words, I guess.
Graduate level class (never took one that was easy, never took one that wasn’t fun)
Engrossing?
Rewarding?
Intensive
I was gonna say time-intensive, myself. But this works too.
Sexy. Does painting nudes get frustrating?
Depends on if they keep flinching away because the paint tickles their skin.
Isn’t that pretty much “subject you really love”?
Or maybe that’s just me. If I liked the subject, I could easily spend tons of time researching and working out problems and even doing extra work to really dig into it and understand it. If I didn’t, 20 minutes of reading was too damn much work.
“Intellectually challenging?”
Science.
Interesting
Education.