I've always been fascinated by language. I remember when I learned that Tolkien had created his languages from scratch, and I thought, "That's really neat! There's no way I could ever do that!" Still, etymology continued to fascinate me.
I've created vocabulary before. Words for things. Slang. I got maybe 3 chapters into Marooned before realizing that this would not be feasible. I found a product that would generate a language for me, but it's rather imperfect. Some of what it gives me is in IPA - the phoenetic alphabet. Some words just don't exist. Some slang translated stupidly. I have found that sometime I have to spend way longer translating things because I have to go back to the etymology of what I want to translate, and then work my way forward using roots.
Karthok has grammatical rules that are consistent, and I do try to follow them. Nounification of a verb, or verbification of a noun have rules, and the suffixes are given in IPA rather than letters. For longer conversations, it's easier to italicize the English, and give clues for the reader to infer that it's being spoken in Karthok, but written in English to simplify reading. There are situations where the characters need to speak a different language in front of others.
Work continues on book 2. I'll begin publishing when it's done, but will likely release only a few chapters at a time. I'm kind of OCD, and I dislike releasing things before they're perfect...but it'll never be perfect. I need to fight with myself to accept "good enough". I don't want to have to go back and rewrite chapters I've already published.