I like the book very much.

I like very much the book you gave me.

I very much like the book you gave me.

I would like very much to thank you.

I would very much like to thank you. 

书上的以上句子都是正确的。

very much作为程度状语可以修饰有程度差别的动词。通常的位置是动词之后，如果动词为及物动词，则位于宾语之后。偶尔very much可以位于动词之前。例如：I very much like the book. 此时强调宾语。

但有时宾语比较长，例如宾语带有定语从句，则通常将宾语移至状语之后，这种现象称为宾语后移，这是英语句子的尾重原则使然。例如：I like very much the bool you gave me. 这个句子的宾语带有定语从句，所以后移到了句末。

如果like的宾语为动词不定式，如果very much位于句末，会被误以为是修饰不定式而不是修饰谓语动词，此时就将very much置于宾语之前或者甚至谓语动词之前。例如：

I would like very much to thank you.

I would very much like to thank you. 

以上二句very much不放在句末，是为了避免误解very much修饰不定式。

虽然以上句子都没有错，但你提问中的句子却是错误的。因为thank的宾语只能是somebody，不能是something。你的错误在于用help作了thank的宾语。