For high school students seeking an entry-level fluid mechanics textbook, recommendations include "Fluid Mechanics: Fundamentals and Applications" by Cengel, which is considered accessible for those with a strong high school-level math background. "Transport Phenomena" by Lightfoot, Bird, and Stewart is noted as a standard text for chemical engineering but may be too advanced due to its use of partial differential equations and tensors. "Fluid Dynamics for Physicists" by T. E. Faber is suggested as a supplementary resource for practical examples and intuitive understanding. "Flow of Fluids Through Valves, Fittings, and Pipe" by Crane is recommended for its practical approach, though it is not a traditional textbook. Overall, starting with Cengel's book is advised for a solid foundation in fluid mechanics.