This dictionary will prove(to be of some use) to you in your

of of +部分抽象名词,=be +该名词的形容词形式.如：
be of use= be useful
be of interest=be interesting
be of value=be valuable
be of help=be helpful
be of importance=be important
of 后面可以加表示程度的限定词,如some,great等.
翻译：在英语学习过程中,会证明这本字典（对你）是有用的.