本 is a measure word, whereas 书 means book. Chinese is full of different measure words to refer to different types of objects, a bit like in English we talk about "a cup of coffee" or "a sheet of paper". In these cases, cup and sheet are both the measure words. Chinese is stricter about their use, though, in that you cannot refer to things without their measure words, but you can sometimes refer to them only by their words. Again, something similar happens sometimes in English. Consider the following dialogue: "Would you like a cup of tea?" "Yes, I'd like a cup." In the reply, the kind of cup we're talking about is understood even though you don't actually mention tea. Have a look at the following resources: https://resources.allsetlearning.com/chinese/grammar/Measure_word https://en.wikipedia.org/wiki/List_of_Chinese_classifiers https://www.youtube.com/watch?v=KIda0ll6ErM

Chinese is difficult in the sense that every words alone can have its meaning. Even if the words are linked as vocabulary, each word in the vocabulary carries a meaning that builds up the vocabulary. I do not know the exact meaning of some words in a vocabulary even I am a native. But to me the word 本 itself has meaning of something related to books or things that can be written in or something written. For example, , in a vocabulary called 記事本(notebook), each word 記, 事 and 本 carries a meaning. 本 here has a meaning of something that can be written in or a book. However, the word 本 is always not used alone, but rather add after words as a vocabulary. It can also be used, as olaf said, as a measure word if used after a number. For example, 一本书 means a book. If you want to write about a textbook, 书 is already sufficient in describing that. 本书 means this book. Hope you find this useful.

書=書本 本=the classifier of books. ex. I have three books. 我有三本書

Okay. I'll try to make it easy for you to understand. In this context,“本” means "this". So “本书” means "this book". And “书” is just "book".

I wrote a text about books. -- 书本 (means general idea of books) I saw one book. -- 一本书 （when together with number, you have to use measure word for different nouns) 本is only measure word for book, itself has no meaning at all. 书itself means book/books, general idea. Chinese words is all about combination of characters to form new meaning. So 书本 means books as general, more often as textboks. There is no word of 本书，but 一本书means a book, 本has to go with a number as it's a measure word. So, "I wrote a text about books" , should be translated to "我写了一篇关于书的文章“。