Dear __________,
You have a pretty good story, and interesting characters -- a good effort for a first novel -- you should be pleased; most people never get this far.
My main criticism goes to the pacing, which is always a tricky beast, and not something most beginners have any idea of how to do. I make the novel at just under 80K words, which is a good length, but the pacing is off.
Not a difficult problem to fix, but it will require another pass before you try sending it around -- in my opinion, which with a dime will get you ten pennies, if somebody wants to make change ...
The quick and dirty course: There are three main ways to move a story: Exposition, dialog, and action. Exposition is the slowest, dialog and action both faster, and the balance among the three is what gives your tale its pacing. Ideally, you want something like an ascending sine-wave, up, down, up, down, all the while slowly climbing to a high point and a leap off the cliff to the end and finish -- like a roller coaster.
If you have too much exposition, it feels slow. Dialog and action can break up the internal monologues and descriptions, but if they are too heavy with qualifiers, they don't do the job and actually make the problem worse, and you don't want stately in an action-adventure novel. There are places where you need lean and mean.
You've probably seen this before, but here are two visual aids for a page layout:
--------------------------------
--------------------------
---------------------------------
-----------------
------------------
--------------------
------------------------
----------------------
and this:
------------
------
-------
--
--
------
-----------
----------------------
--------
You see the difference -- shorter sentences, shorter paragraphs, choppy exchanges, play faster because they are literally faster to read. You have fewer words on a page, and if you use punchy terms -- smash, stab, thrust, whack, like that, to ramp up the imagery, the pages get turned faster, which imparts a sense of speed to a reader.
Want them to hurry along? Write short and tight. If you want it exciting, moving them along faster helps.
Chapters are another way to alter the pacing -- a longish chapter followed by a shorter one, followed by a medium-length one -- don't make them all the same length. Might average eight or ten pp each, but now and then, a three- or even a one-pager is valid and can pick up the pace.
There are places to walk, and there are places where you want to run like a scalded cheetah. You don't want a steady pace throughout. Sprint, jog, walk, stand still, sprint again.
No reason you should know this, it's a fairly advanced writing skill and not easily taught, but that's what you need to do.
While the writing itself isn't bad, most of your text is homogenized, i.e., the paragraphs and sentences tend to be the same length and this makes for a kind of slow-jog monotone in delivery. You don't want this. (Pick a couple pages at random and look at them; what I mostly see is: Four or five lines to a graph, seven or eight graphs to a page. This is okay for a few pages, but more than that, readers will start getting bored. You need to vary it.)
Once you see this, you'll wonder how you missed it -- and you won't miss it again.
Break them up. Use active voice and not passive. Instead of phrases like, "Heading up the mountain, he ..." say instead, "He headed up the mountain." Simple past tense flows better. Clean and crisp are the way to go. Don't worry about style, just tell the story. Style comes on its own.
Fix this, you are 85-90% of the way there.