Books are allowed more wiggle room than film or television, which is why Middle Grade and Young Adult books contain more mature topics than what appears in many shows and films for that same demographic.
Similarly this could be said of comics, which often depict much more violence and mature subject matter than films or cartoons aimed at the same young demographic.
Prose works that rely heavily on internal monologues are hard to adapt to film or television mainly because depicting one often stops a movie dead in its tracks.
Stories with a Tomato Surprise plot may be difficult to adapt to a dramatic medium as it is harder to hide the twist element (especially if The All-Concealing "I" is involved) without tactics that are so obviously artificial that they tip off the viewer in themselves.
Video games have a completely different way of writing than film (assuming they haveplots), particularly being that adapting a game into film inevitably removes the core component of a game (the gameplay) which is a component in why Video Game Movies Suck.
Visual Novels tend to suffer from this as they usually involve separate routes depending on the protagonist's choices that are understood by players to essentially be different universes, which most mediums don't deal with unless the story is explicitly sci-fi. There are three main ways of dealing with this:
1) excise any inconsistent content (usually, the romantic stuff) and adapt as much of the routes as possible (Kanon)
2) excise no content and just accept that the protagonist will act in ways that seem chaotic and/or immoral (School Days)
3) take the alternate universe route and essentially turn the adaptation into an anthology series (Yosuga no Sora) This is even weirder for VNs such as CLANNAD and Little Busters! that explicitly use the visual novel mechanics as part of the story - in Clannad, there is an urban legend that an orb of light capable of granting a wish will be created when someone experiences a moment of true happiness, and completing each route spawns a light orb on the home screen which becomes relevant in the true route, and in Little Busterseach route is a result of Kyousuke turning back the timeline in this artificial world he created to try and give Riki and Rin enough new experiences that they'll be able to grow up and become able to take care of themselves. The Clannad anime keeps this pretty subtle, and just leaves out the orbs created from the routes which weren't adapted (Kyou and Tomoyo's for being explicitly romantic and contradicting the true route, plus two more just for time), while Little Busters covers this plot point by depicting only Kurugaya's route (also necessarily romantic) in the 'alternate universe' format.
Generally-speaking, a good number of rock operas fall victim to this trope, as the medium of a music album features a number of conventions and stylistic permissions that wouldn't be possible in a more visually-oriented format.