I have question about GTD methodology. What should I do with something that can't be done in simple step. For example: "Read book <X>" or "Write Essay" or "Prepare patent documentation". They looks like Next Action but will take much more than one day or even week.
Next actions aren't inherently about simplifying - they're about having placeholders to denote the next thing that has to happen to move something forward. The idea is to present you with a menu of the available things you *can* do to move toward your goals, and let you choose as appropriate.
*Personally*, I would call "read book" a next action by itself. The only real restriction there is the context, i.e. "am I someplace where this book also happens to be?" If you're in a place where the book is, and you have a persistent way to mark progress (like a bookmark), it doesn't need to be any more fancy than that.
If you need to break it down into pieces/parts to motivate you, I would still have "read book" as the next action, possibly with a supporting checklist that lets you list all the chapters and check them off. Or you can go crazy with software GTD implementations and set up a task that repeats (the number of chapters in the book) times. That way you can read a chapter and check it off.
DA has mentioned in some of his material that some of his next actions say things like "draft article". Again, as long as you're in a context where you have the ability to write, and there's nothing else blocking the action (research, etc.), "draft article" is a perfectly-fine next action.
"Context" and "next action" are the key things here, though.
"Prepare patent documentation" isn't a next action unless you could sit down in some context, right now, with the material readily at hand, and do the job. If you need to get information from Fred to prepare the documentation, "prepare patent documentation" is a project, and "get material from Fred" is the next action. And technically, if you don't even know how to contact Fred, "get Fred's phone number and/or email address" is the next action. Of course if you don't even know where you would look for that contact information, "contact supervisor to find out who has Fred's information" might be the next action. And once you email your supervisor, "Waiting for Dave to get me information re: how to contact Fred" goes on a "waiting for" list, and your forward momentum on the project stops until that issue is resolved somehow.
My problem with this things that I will start to ignore them after certain period of time
This is what a weekly review is intended for. You go over *everything*, and make sure that nothing is getting ignored or falling through the cracks. I'm not great at this myself, but it's a critical component of making the system work.