and look!
You can use ЛИ in three places of senstenses У НЕГО ЕСТЬ УЧЕБНИК?
1. Есть ли у него учебник? (question about ixisting of his textbook)

2. У него ли учебник? (question about place) (who has a textbook? Is he?)
3. Учебник ли у него? (question about a textbook) (what does he have? Is it textbook? OR I know that he has something.. Book? Textbook? Notebook? Mmmm.. I think this is a textbook... And I use ЛИ for showing of my guess)

Now without ЛИ:
1. Есть у него учебник? Or у него есть учебник? Sense's ABSOLUTELY same with sentense with ЛИ.
2. У него учебник? Sense's the same.
3. Учебник у него? Here sense changes... now this is like у него учебник? I ask: where is a textbook? has he got this? I don't know where.. I don't know he has somethig or not..