Yeah, also even if V is still the instigator in the novel, a lot of the chaos and unraveling of the fascist state is because of the different parts of it manouvering against each other and trying to seize power, V is only tangentially involved in killing the head of state, he's just assassinated by a relatively random woman who has been victimized by the system.

Also the aftermath is shown as having very harsh effects on people even if its good that the fascist state has collapsed, one of the last things we see is a woman being forced into selling herself for food cause all of hers was stolen, which might be intended as a kind of karmic thing cause the woman was one of the main political schemers in the fascist state but its still fucked up and something that would happen if the state collapses with no real structure or organization to follow it. Contrast that to the movie which just kinda ends in a peaceful demonstration and the fascist soldiers refusing to gun down a crowd.