It is a fast and portable binary serializer designed to be easily used on a wide range of .NET platforms. AqlaSerializer can store objects as a small in size binary data (far smaller than xml). And it's very CPU effective.
Basically it's a fork of well known protobuf-net project. Protobuf-net tries to maintain Google Protocol Buffers format compatibility and unfortunately has issues with handling some very common .NET specific features.
AqlaSerializer project main goal is to support all common .NET features like nested collections and multidimensional arrays.
Another difference is that protobuf-net serializes data but AqlaSerializer is intended to serialize objects. What the difference? Data serializers don't care much about language runtime specifics like references, inheritance, etc. In contrast, an object serializer should take such things into account.
It is a free open source project in which you can participiate.