Deep Learning, Ian Goodfellow, Yoshua Bengio, Aaron Courville, 2016 (MIT Press) - A foundational textbook covering the mathematical and conceptual basics of neural networks, including detailed explanations of forward propagation in feedforward architectures.
Neural Networks and Deep Learning, Michael A. Nielsen, 2015 (Determination Press) - A freely available online book that offers a gentle yet mathematically thorough introduction to neural networks, with clear steps for forward propagation.