Error Spotting – Choose the part (A–D) that contains the grammatical error, or choose No error if the sentence is fully correct. Sentence (parts correspond to options below): A) This is one of B) the most interesting book C) I have D) ever read.

Introduction / Context:
The focus here is number agreement in the partitive construction one of + plural noun. After one of, the following noun must be plural because the reference is to one item from a set of many.

Given Data / Assumptions:

• Partitive opener: one of
• Adjective phrase: the most interesting …
• Head noun written in singular: book

Concept / Approach:
Structure: one of + the + superlative + plural count noun. Therefore, book must be books.

Step-by-Step Solution:

Verification / Alternative check:
Parallels: one of the best movies, one of the greatest players. Singular would be unidiomatic.

Why Other Options Are Wrong:

• A) Deictic phrase This is one of is fine.
• C) Relative clause I have … introduces experience and is grammatical.
• D) ever read is a standard intensifier with present perfect.

Common Pitfalls:
Writers sometimes let the nearest adjective distract them from the number marking of the head noun. Always pluralize after one of.

Final Answer:
Option B contains the error. Use the most interesting books.