A couple of things before the review
-All the objects added by you should have a TR_mx_ prefix. Not considering it here cause it's not a claim, but still.
-The topic name could be better :P. Again, not really considering that right now, but an FYI.

Review:-

As a bit of a general advice, I suggest using a bit more commas. There's no spoken lines, so the player should be able to guess the tone from the writing itself.
Topic "Deliver a dirty dirty book"
    -This book is for me? Thanks, %PCName. I have been a bit short tempered lately.. perhaps a bit too much. If you could tell Mo'nahl that I forgive his delayed delivery it would be appreciated.
    '..' should always be '...' for consistency, and a comma after delivery would flow better.
    -And you say he has forgiven me? This pleases me mortal. Here, take this. I don't have need of it anymore. I've got to be going now.
    'He has forgiven me? This is great news, mortal. ...' something like this flows better than starting the sentence with And imo, and the comma before mortal also makes the flow better. 
    -"...Gordol has been a bit on the down side since the delivery has been taking some time now. ..."
    the 'since the delivery has been taking some time' part doesn't flow very well. Try to come up with better wording. "Gordol has been a bit down lately. I suspect it is because of the delayed delivery." is my try.
    also:morrowind rarely uses the word 'dimentions'. 'plane' is much more used. (You can check the usage with edit->find text)
    -"Yes, deliver a book. A dirty one. So what is it gonna be? Answer me mortal."
    This feels too hasty, if that makes sense. "Yes, I need(or want) you to deliver a book. A dirty one." in of itself works. the next few lines feel like he's asking the same question three times. It could work with some other changes though, experiment and see what works in the game's atmosphere.
Greeting 5
    -"Hey, you! Yes you mortal. You could deliver a dirty dirty book couldn't you?"
    A comma after you and book will flow better.
    -You don't need to addtopic every time it comes up, only the first.
Playtestng notes
    -You need to have dialogue for every journal entry for "deliver a dirty dirty book" (For example it doesn't have dialogue for journal 10 or 20) even anything basic is ok, but the topic shouldn't disappear from the daedroth
    -You need a Menumode check so that the timer doesn't run out in-dialogue or the inventory screen.
    -Maybe set the fight of Gordol to 0 after he gets the book?
    -Might want to make Gordol a little less OP :P.
    -His disabling feels a bit too... abrupt. Have him cast an intervention spell or something first for the effects? 
    -The daedroth still asks you to deliver the book if you killed him before the quest starts.
    -The journal should give some indication of the time limit.
    -Gordol should prolly have NoLore so he doesn't talk about random topics.
    -The book the daedroth gives you is the original lusty argonian made, not the one you made.
    -You should also give some dialogue to the daedroth for when the quest finishes after you read the book and/or a warning before not to read the book.
Scripts
    -You don't need to positioncell the daedroth outside the world, you can just use the `disable` function.
    -You use both tr_m0 and tr_m1 for scripts. The script names should be tr_mx_Gordol and tr_mx_Mohnal ideally. Also an ideantifier of the quest it's in would be ideal too. (TR_mx_acd_name with acd being the short form of a chary delivery)
    -Just a good practice: Using standard names such as Timer and Control/State/DoOnce is better than custom names.
    -As I already stated above, a menumode check is needed for the timer.
    -I don't think the script will work in the book. You can drop the book, then read by activating and it won't give you the spell. The correct way would be to copy-paste the same thing in the OnActivate block that is in the OnPCEquip Block.

Playtests
    -If you kill gordol before the quest starts, the journal still updates with "I failed to deliver the book.". Instead, the dialogue that gives the quest should be filtered to the death so the daedroth doesn't give you the quest when gordol is dead.
    -If you give the book, then kill Gordol, the journal still is "I failed to deliver the book.", which is kinda wrong. Something like "Gordol is dead." might be better suited. (Add a new journal for this specifically.)
    -I'm not sure I understand the book-giving. Mohnal gives you the book, then you give it to Gordol, and then Mohnal somehow gives you the used one. It's slightly odd.
Dialogue 
    DELIVER A DIRTY BOOK
    -"...Oh and don't read the book please."->"Oh, and please don't read the book" flows better/is grammatically correct.
    -Gordol's first entry should check for if the player has the book(and there should be another entry for if they don't)
    GREETING 5
    -"What is this about? You say you're here to deliver a dirty book?" this doesn't need the addtopic
    JOURNALS
    -Just a QOL thing, but the journals should be in order of their indices.
Scripts
    -mx was shorthand for m0/m1/m2 my point was that they all should have the same number, see https://www.tamriel-rebuilt.org/content/resource-trmainland-cs-id-guidel... for more info.
    -Due to the return above in tr_questtimer, the getpcsleep will never work. You need to remove it, and move the `set Timer to ( Timer + GetSecondsPassed )` part inside a menumode == 0 check.
    -Right now it sets the DoOnce to 1 instantly when TR_questtimer starts AND the stopscript also stops it in one frame, so the script doesn't work at all. You should put the set DoOnce to 1 thing inside each block. You should also put a check so that it only stops the script when the journal is >20.
    -You should playtest the quest whenever you change something significant, so you can make sure everything works.