"Her Story" is in the minuscule subset of narrative-driven video games where I feel like my agency contributes to the experience. Much like "Papers, Please" before it, I exist not as the character on screen but as the main actor in "Her Story", text-searching an interrogation video database for...whatever I want to know. There is no straightforward end state to the game, and the number of questions you answer depends entirely on your willingness to dig into the backstory of the interrogated. No one is making you do this. It's possible, by sheer luck, to close the whodunit of the case in 5 minutes just by searching the right word (even if Sam Barlow, the game's designer, did a remarkable job engineering methods to keep this from happening in every instance), but that's only the most obvious question the world behind "Her Story" inspires. The game draws heavily from the stylings of Serial, the open-ended murder mystery podcast from Sarah Koenig, and it shows. It's marvelous.
It took me a little under 4 hours to get what I needed out of the game, with one short break in the middle.
Recommendations: play when it's dark, with some amount of alcohol (not too much), and write your findings and hunches down on actual physical paper. The User Tags feature is handy, but not even close to as satisfying as flipping through a journal of scribblings.