Great featureful and easy to use Book catalogue manager. Imports books by barcode scanning (if its a new-ish book, ISBN is encoded) or lookup by ISBN/ASN/Title/author/etc. Syncs with GoodReads but is much easier to use. Exports data as well. Fully open source, code is on GitHub. Used to be on google play store, an older version is on Amazon app store, this version fixes a problem syncing with GoodReads present in the amazon one.