As mentioned, Pickles create fantastic documentation, in various formats (HTML, Word, etc), and links nicely with SpecFlow results. I have yet to try it but I'm sure Serenity BDD is worth investigating too, given the involvement by John Ferguson Smart.
Neither (AFAIK) provide any of the visual story mapping that SpecLog does though. The closest equivalent I get to that (and it's really not that close) is the tree explorer in your dev environment of choice, using folders to group your features hierarchically.
There are some nice options for visual story mapping, e.g.
featuremap.co,
storiesonboard.com,
cardboardit.com. They usually export to various file formats and maybe integrate with some issue trackers. They also charge.
I've never used SpecLog, but I'd say if you can afford it, go for it. It looks super slick and integrated. If you can't, you'll need to get a bit Rube Goldberg and mix and match various tools.
What I'd love is a visual story mapper, that links to feature files and
links to github issues. And is free and open source. I can dream!