You can read a book whenever you want. To get book club going, we need to allow additional time for everyone to get their options in order, hence why we chose two books straight up, and already the next book thread is in progress... so we have a constant forward list of defined books for reading.
The discussion is the important aspect, as that is where we need to set boundaries I think, as you don't want people spoiling it for others by posting information ahead of time in discussion.
Someone who has The Tigers Wife already, I'm sure could say how many chapters there are, and provide a rough suggested reading rate that we should follow, before the rest of us get the book.
The whole idea is that this doesn't become stressful to anyone, nor is anyone advantaged or disadvantaged, hence... read the book if you have it already, but don't disadvantage someone who doesn't by posting anything about it, or ahead of the agreed discussion rate that allows acceptable time for everyone to read x chapters, discuss... read x chapters, discuss, etc.
Quite honestly, it would be very disappointing IMHO if someone started posting ahead of the reading rate, or eluding to things ahead, spoiling the read for others... hence, we need to define the discussion rate.
To my knowledge, a book club who meet in person have a set timing they meet, weekly or monthly, etc. They pick their book, every reads it in their own time. What doesn't happen, is people start having earlier discussions on the content read, instead that is left to when they collectively meet and share their interpretations, experiences, etc, of the book.
To me, that is the idea that should be followed here... so people can read whatever they want, when they want, but we discuss the book in some type of defined process so that nobody is spoiling something for another.
I have no doubt there are people here who can read 400 pages in a day. Me... I can't, nor do I have the time to dedicate a day for it, and I can't speed read. My inability is not disadvantaging the speed reader to read the book now. Nor is their speed reading disadvantaging me reading slowly, because neither of us can respond about x chapters until y period.
I think that was the initial interpretation taken from our first ever discussion in the chit chat thread on whether to have a book club or not.