From README.md:
Tensorflow implementation of message passing neural networks for molecules and materials.
The framework implements the SchNet model and its extension with edge update network NMP-EDGE as well as the model used in Materials property prediction using symmetry-labeled graphs as atomic-position independent descriptors.
Currently the implementation does not enable training with forces, but this might be implemented in the future.
For a more full-fledged implementation of the SchNet model, see schnetpack.
The main difference between msgnet and schnetpack is that msgnet follows a message passing architecture and can therefore be more flexible in some cases, e.g. it can be used to train on graphs rather than on structures with full spatial information.