Verin's book wasn't entirely necessary, at all in fact. Seaine's group had come up with a pretty much foolproof method that Egwene, while she somewhat disagreed with the methods by which they went about it (namely the 4th oath), agreed was practical and necessary. Verin simple gave Egwene enough warning to prevent quick escapers like Sheriam, although if she hadn't known Sheriam, chances are she would have been prepared for anyone to escape, and the same would have happened--namely, Sheriam tries to bolt/channel, and is caught. The Oath Rod technique would have worked regardless.