Eragon was fantastic, Eldest a bit boring but a good reading. Brisingr was only boring... and this Inheritance is the worst in everything. Childish ending, rushed writing, boredom...
It doesn't cost a lot, so I'm not angry for having bought it, I'm just disappointed for it wasn't good enough.
Harry Potter 7th book was very good compared to the others, the best of the 7. But in this case, Inheritance was the worst.
I could suggest you to go and read just a storyline of what happens in Inheritance, but it would disappoint you anyway, because the whole story is so childish.
Now that I know all this, I can say that Eragon was the only book worth reading. It is full of action, people, cities, emotions, happening things and battles. Inheritance needs to be forgotten.