Harry has been burdened with a dark, dangerous and seemingly impossible task: that of locating and destroying Voldemort's remaining Horcruxes. Never has Harry felt so alone, or faced a future so full of shadows. But Harry must somehow find within himself the strength to complete the task he has been given. He must leave the warmth, safety and companionship of The Burrow and follow without fear or hesitation the inexorable path laid out for him. --front flap
Reading the series again after 25 years made me realise how much I didn't get the first time and how much was altered for the movies.
From all books I liked "The Order of the Phoenix" the least. Not sure why but I thought it quite chewy to read through. Not as gripping or thrilling as the others.
Nonetheless, I love the series. Guess, I will read them again in 20+years or so ;).