I have spent a bit of time trying to work out the events. Below is what I have. Some of the events map to awards (table Achievement) through the Rules table. I have posted this before, but this is probably a good place for it to reside.
Code:
Id Description
0 Sync with Kobo - One for each book synced, but only when a new book is downloaded? LastOccurence is updated
3 Open book
4 Started a digital library - One for each kepub
5 Finished book
46 Turn page - Event count = number of pages turned
47 Read all night
48 Read all night
63
80 Page Turner ("Read two hours straight")
1001 Read 12am-1am
1002 Read 1am-5am
1004 Read 7am-9am
1005 Read 9am-12am
1006 Read 12pm-2pm
1007 Read 2pm-4pm
1008 Read 4pm-6pm
1009 Read 6pm-8pm
1010 Read 8pm-10pm
1011 Read 10pm-12pm
1020 Open book?
1021 Close book?
For events 1, 36, 52 and 79 there seem to be only one row.
There are some inconsistencies. Both events 46 and 80 count page turns, but they don't match. The count for 80 is always less than for 46. It is possible that 46 is counting screens and 80 page numbers. The value for 46 is what is on the stats screen for the current book.
When I have looked at ExtraData, it tends to be made up of a series of timestamps. I suspect that for events like 1020 and 1021, it is a list of the times when the event occurred. The pairs from the two events might be used to calculate the minutes per session and hours read. The only problem with that, is that the counts don't match for the book I am currently reading. I am confident of the meaning of the events, but there seems to be occasions when the close is not recorded.