Just go slowly, one clause as a time (and the way you transcribed the passage makes it hard to separate clauses, which is responsible for part of your confusion). Here's how I would approach it (and mikkih can correct if I stray XD ):
18歳でR小説大賞準入選 At 18, runner up for Taisho Novel Award (by analogy with
http://en.wikipedia.org/wiki/Manga_Taishō but you can tl it your way too)
翌年M大学文学部入学後デビュー The following year, enrolled in the Literature Department of M University and debuted afterward
This is the difficult sentence:
序盤から怒涛の展開を見せる作風でデビユー作は「1Pでも読み飛ばすと登場人も物が3人も死んでいる」と評された
Two clauses here:
1) 序盤から怒涛の展開を見せる作風で
2) デビユー作は「1Pでも読み飛ばすと登場人も物が3人も死んでいる」と評された
The main clause is the second one, since it has the topic (conveniently marked by は)
デビユー作は「1Pでも読み飛ばすと登場人も物が3人も死んでいる」と評された the pattern here is very simple: デビユー作はXと評された = debut work was appraised as X
You're already close enough as far as the meaning of the quote goes, but more precisely I would put it as "If you skip even one page, three characters are already dead" implying that there are about three characters killed off on every page of the novel.
Now with the supporting clause, where you had the most difficulty, you can go one word at a time, from the end.
作風で the particle de indicates that this is the reason the debut work was appraised in such a way. 作風 means "literary style". So we can say so far: With its literary style, the debut work was appraised as "If you skip even one page, three characters are already dead".
The word before 作風 is a verb, so we can see that the whole fragment 序盤から怒涛の展開を見せる is a subordinate clause that describes 作風. If you were to turn it into a main clause where 作風 is the subject, you would say 作風は序盤から怒涛の展開を見せる. The basic structure here is your regular subject/indication of time/object/verb, i.e. 作風は/序盤から/怒涛の展開を/見せる. The subject is "literary style" and the verb is "shows". The object is this whole 怒涛の展開, where the noun that serves as the subject itself is 展開=development, and 怒涛の is acting like an adjective describing the development. Now, this 怒涛 is somewhat rare and it's difficult to get an accurate sense of its meaning. The dictionary says (1) surging waves; raging billows; (2) leaps and bounds. If you're describing development (of a novel's plot), then clearly the meaning used is "leaps and bounds". So 怒涛の展開 becomes "development by leaps and bounds". Finally, the time indicated for when the action takes place is 序盤から. The meaning of 序盤 is "opening, early stages" and から is "from". When talking about about a novel, you can say "from the very first pages". So putting this sentence to together, you get "Literary style shows development by leaps and bounds from the very first pages".
Now transform it back into a subordinate clause and attach it to the main clause: With a literary style that shows development by leaps and bounds from the very first pages, the debut work was appraised as "If you skip even one page, three characters are already dead".
Now rephrase it into natural English and you're done.