Poul Anderson's Time Patrol series presents not multiple timelines but a mutable timeline. A close reading of the Timeline shows some bracketed events. These are remembered but prevented. There is also a period of "instability." Potentially, other timelines flow from this period. Such timelines could be displayed separately and a time traveler might pass through the instability into an alternative timeline.
This series has to be the subtlest treatment that there has been of the time travel causality violation paradox. L Sprague de Camp's Lest Darkness Fall and Ward Moore's Bring The Jubilee both succeed because each confines itself to describing a single time traveler initiating a single divergent timeline.
However, Anderson instead wrote a long series about a large organization, based throughout history, preventing or rectifying causality violations, and he managed to do this while at the same time avoiding any overt incoherencies or contradictions, unlike alternative attempts. His unstable space-time periods are endlessly fascinating because there is no way to pin down exactly what has happened or is going to happen in such situations.