My sub purpose in playing that game is to improve my English. Despite the fact that I have the case like yours (getting tired while reading) I want to keep determined and achieve my goals. Finishing so complex plot with reading every single line will be a great equivalent of an expensive language course ;)
And maybe a little offtopic: I will start learning French this October as it is my chosen second language on my studies :)
That is a nice goal. Actually, I learned english when I was a kid by playing videogames. It allowed me to get top grades in english during all my studies :-) And I never got the feeling that I was actually working to learn english, I was just playing the games I enjoyed and trying to understand what I was supposed to do :-D
But right now I don't have much time to play, and I've got so many games on my backlog... I really want to play Planescape, but if it gets tedious because of all the reading, I'm afraid I might skip it for another game in my list and miss something, hence the french patch. If it's THAT great, though, I might replay it in original version !