Kaplan notes are the absolute best review source for USMLE. There is no doubt that it is a high yield, and one should not attempt USMLE without preparing from them. 

Features of the Kaplan USMLE Step 1 Lecture Notes 2020:

Kaplan Medical’s USMLE Step 1 Lecture Notes 2020: 7-Book Set offers in-depth review with a focus on high-yield topics in every discipline—a comprehensive approach that will help you deepen your understanding while focusing your efforts where they’ll count the most.

Used by thousands of medical students each year to succeed on USMLE Step 1, Kaplan’s official lecture notes are packed with full-color diagrams and clear review. The 7 volumes—Pathology, Pharmacology, Physiology, Biochemistry/Medical Genetics, Immunology/Microbiology, Anatomy, and Behavioral Science/Social Sciences—are updated annually by Kaplan’s all-star expert faculty.
The Best Review

• More than 2,700 pages covering every discipline you’ll need on this section of the boards
• Full-color diagrams and charts for better comprehension and retention
• Clinical correlations and bridges between disciplines highlighted throughout
• Chapter summary study guides at the end of every chapter for easier review

Up-To-Date Content

• Clinical updates included in all 7 volumes to align with recent changes
• Organized in outline format with high-yield summary boxes for efficient study