GRE

Harvard University generally does not publish specific GRE cut-off scores for its programs. Instead, they use a holistic review. However, for MS admission in Harvard, you need to score between 155 to 170 for Verbal and Quantitative, and 4.0-5.0 for Analytical Writing.

Beyond USA, GRE scores are widely accepted for graduate programs in over 90 countries. Top study destinations like Canada, United Kingdom, Australia, Germany, Singapore, France, and the Netherlands. Many universities in these countries ask for the GRE scores at the time of Master's, PhD, and MBA admissions. Always check specific university requirements.

Here are some of the best books for GRE exam:

1. GRE Prep Plus 2025 by Kaplan Test Prep
2. Official GRE Super Power Pack by Educational Testing Service (ETS)
3. GRE Vocabulary Flashcards by Kaplan Test Prep
4. 5LB Book of GRE Practice Problems by Manhattan Prep

These books are easily available online and covers diverse range of GRE topics.

You need to keep few things in mind at the time of buying GRE books such as:

• Official Content: Prioritize ETS study materials or reputed publishers.
• Clear Explanations: Concepts mentioned in books should be easy to understand.
• Practice questions: Choose the books with more pratice question. Also, it should be detailed answer explanations.
• Up-to-Date Content: Pick only the latest edition books which reflecting the current test format.
• Reputation: Check reviews from other test-takers.

It totally depends on the authenticity of your free online study materials. If it is from ETS's official website or any reputed publishers, then it is valuable. However, taking help of these courses only can put you in trouble. Official prep books often provide a more structured, comprehensive, and in-depth learning experience. It will be smart decision if you use both.

Here are some of popular books which offer practice tests for students

• Official GRE Mentor Prep Course by ETS
• POWERPREP Online by ETS
• POWERPREP PLUS Online by ETS
• Kaplan GRE Prep Plus
• The Princeton Review GRE Premium Prep

All these books have good reviews by students as it offers lessons, contents and quizes related to th GRE.

Yes, there are many preparation books come with GRE practice test sets. If you will buy online edition of such books you will get access to online pracice tests with computer adaptive simulations. It is suggested to use official guide and study material by ETS for getting access to ETS's POWERPREP software.

Choosing the best books for GRE prep is not a tough task. You need to keep few things in mind:

1. Choose only official ETS materials for accurate question types. 
2. Look for books that explain GRE concepts clearly and offer plenty of practice questions with detailed explanations.
3. If the books cover all sections: Verbal, Quant, and AWA then its good or you can buy section-wise books of reputed publishers.
4. Read reviews to see what other students found helpful for their learning style.