I am looking to recall a book I read 20 years ago. 

* A journalist/anthropologist man (human) studies aliens.
* He uses various techniques to get close to hard to study aliens.
* He starts to use tech to modify his body so he can get closer to the aliens or study them better.
* By the end of the book his body is so modified he no longer sees himself as human, and indeed has more or less forgotten his human roots.
* It was in English.
* "by the end of the book" he was modified and no longer saw himself as human (ergo... nothing happened after that, that was the end of the book).
* His motivations are (journalist/anthropologist) he was there to simply study the aliens (there may have side stuff to that plot, I forget).
* How he modified himself (to the best of my memory) = technology. (surgery, and part grafting and other I do not recall).
* What he learned from the aliens (their physiology and culture).
* Where was he studying them? = On their home worlds.
* How did he get access to them? = I don't fully recall (space flight seemed to be a thing, but unimportant to the plot).
* Was their presence known to other humans? (Sorta, kinda like Jane Goodall, he would go find new species and study them, I don't recall how the rest of the books universe heard of the aliens.)
* It was a standalone book, not a part of a series.
* It was fairly short, maybe... 350 pages or so.
* Each chapter showed the protagonist's mind having slightly more trouble with human concepts or speech patters.
* It is somewhat like reading the protagonists' 'journal'.