Online reading terms

Updated October 13, 2026. Seller: Sylvan Labs Company Limited. Support: [email protected].

What you purchase

Each book costs USD 2.99 including applicable taxes. Chapters 1 and 2 are free. A one-time purchase unlocks all remaining chapters, appendices, and included revisions of that book for personal online reading while this service is operated. There is no subscription, printed shipment, or download package. Purchasing one book does not unlock other books.

Access and recovery

Our server verifies payment before granting access. Purchases belong to your browser session. Save your private recovery code and order number to restore purchases on another browser or device. The recovery credential expires after one year without renewal; active paid reading renews it for another year. Credential expiry does not delete your purchase. Contact support with your order number if you lose access. Do not share or publish the recovery code.

Payment, refunds and support

Airwallex processes payments. If payment is pending, access opens after confirmation. Contact support for duplicate charges, unavailable paid chapters, or access problems. Refund requests are handled according to the issue and applicable consumer law; your statutory rights remain unaffected. Refunds or reversed payments remove the corresponding reading access.

Personal use

You may read and use the exercises personally. You may not resell, publicly redistribute, or publish the book text without permission. Reflective exercises are educational and do not provide predictions, medical treatment, or professional legal or financial advice.