The palindromic NisiOisiN fathered both the Monogatari series and the Katanagatari series, and it certainly shows: from the ways that the characters interact with each other to the bordering-on-bizarre-but-ultimately-endearing plotlines, if you liked Koyomimonogatari (or just the Monogatari series in general), you'll like Katanagatari.
However, just because you liked Katanagatari, that doesn't mean you'll like the Monogatari series--it's a one-way street. From one viewpoint, you could call Katanagatari a more grounded, less perverse, non-harem, non-surreal and less condensed version of Monogatari. in other words, if you liked the concept of the Monogatari but didn't care for its execution, you'll likely love Katanagatari.
From another perspective,
you could say that Katanagatari is 'less' than Monogatari. However, if you've ever heard the phrase, "less is more", then I can assure you that it certainly applies here. While Katanagatari is far more straightforward in its narrative, that also allows it to focus on and improve its other aspects--particularly the ones that I felt Monogatari fell short in.
Regardless, I urge you to at least give Katanagatari a try if you're a fan of NisiOisiN and his works because it is certainly one of his better ones. If you're a fan of Katanagatari, on the other hand, and are interested in the Monogatari series, Koyomimonogatari is not the place to start. Work your way up from Bakemonogatari all the way to Owarimonogatari before getting into Koyomimonogatari; it's a series of side stories that take place in between the main events that occur in the parent stories. read more 
