immerse 是及物动词，必须后接宾语。本义为把某物浸入液体中。引申义为某人把自己投入到某项工作中，用反身代词作宾语或用被动结构。例如: 

She had immersed herself in writing short stories.

She was immersed in her work.

所以，你的句子 I am immersing in reading books.为错误。可以做如下修改：

I have immersed myself in reading books.

I'm immersed in reading books.