The two constructions don’t have the same meaning.
Je ne lis rien de monstrueux
would mean that there is nothing "monstrous" in what I read, on the opposite
Je ne lis rien que de monstrueux
would mean that I don’t read anything that is not "monstrous"
The latter construction is not often used because you would expect a noun with this kind of construction ("ne…que" meaning "only").
Je ne lis (rien) que des monstruosités (I only read montruous things).
EDIT: concerning the sameness of the construction, it would be more clear if you looked at the sentences the other way around. Do not compare que de + adjectif and de + adjectif, but look at the cases when the use of "de" is needed before the adjectif. If you consider the two sentences you will see the you have to add "de":
Tout ce que je + verbe + de + adj
Je ne + verbe + que + de + adj
Remark : One construction where you could also find "que de" alone is to introduce an emphatic sentence. "Que de" is then used for "So many"
Que de belles années ai-je passées là-bas!