The Financial Risk Manager (FRM) Exam is a rigorous exam and  tests your knowledge on four topics:

• Foundations of Risk Management
• Quantitative Analysis
• Financial Markets and Products
• Valuation and Risk Models

For each of these topics, GARP prescribes reading material which is essentially a collection of chapters taken from different books. To prepare for FRM exam you can buy these readings and that's sufficient. However, it may be a good idea to buy the full books as they are a very good set of books which will always be good reference for any risk manager. Below I have listed all the books that you need to prepare for FRM Exam Part 1.

Foundations of Risk Management

Modern Portfolio Theory and Investment Analysis

Portfolio Theory and Performance Analysis (The Wiley Finance Series)

Risk Management in Finance: Six Sigma and other Next Generation Techniques (Wiley Finance)

Financial Risk Management: A Practitioner's Guide to Managing Market and Credit Risk (Wiley Finance)

Quantitative Analysis

Mathematics and Statistics for Financial Risk Management (Wiley Finance)

Introduction to Econometrics (3rd Edition) (Addison-Wesley Series in Economics)

Value at Risk: The New Benchmark for Managing Financial Risk, 3rd Edition

Options, Futures, and Other Derivatives and DerivaGem CD Package (8th Edition)

Financial Markets and Products

Options, Futures, and Other Derivatives and DerivaGem CD Package (8th Edition)

Derivatives Markets (3rd Edition) (Pearson Series in Finance)

Commodities and Commodity Derivatives: Modelling and Pricing for Agriculturals, Metals and Energy

Financial Institutions Management: A Risk Management Approach (McGraw-Hill/Irwin Series in Finance, Insurance and Real Estate)

The Handbook of Fixed Income Securities, Eighth Edition

Managing Credit Risk: The Great Challenge for Global Financial Markets (Wiley Finance)

Valuation and Risk Models

Understanding Market, Credit, and Operational Risk: The Value at Risk Approach

Options, Futures, and Other Derivatives and DerivaGem CD Package (8th Edition)

Fixed Income Securities: Tools for Today's Markets (Wiley Finance)

Managing Credit Risk: The Great Challenge for Global Financial Markets (Wiley Finance)

Measuring and Managing Credit Risk

Internal Credit Risk Models: Capital Allocation and Performance Measurement

Measuring Market Risk

Risk Management and Financial Institutions, + Web Site (Wiley Finance)

Value at Risk: The New Benchmark for Managing Financial Risk, 3rd Edition

You can purchase these books from Amazon by clicking the links above.