Google Raul Pacheco Vega - he has a great blog and demonstrates this spreadsheet he's designed in which he organises readings thematically, with column for the main point of each, his critiques, study site, etc

Haha. I remember feeling this way for the first six months of PhD. Don't worry - you'll get busy soon! That said, you can be smart about how you use this time. Make sure your work is structured: you can map out the issues/conversations in your field that you need to be familiar with and write up good notes on the relevant papers you read; brush up your methodological competence; this might be a good time to look for some early teaching opportunities - perhaps you can give a guest lecture somewhere?