There have been problems with the distribution of Visible Mantra caused by Lulu which seems have set my book to not published. How they did that, and why they have responded to my inquiries (they have responded to one customer and told him I'd closed my account!) I do not know. However I have republished the book and it should be online again soon. My apologies for the confusion, but it was entirely out of my control.
The book can be purchased right now by following this link: http://www.lulu.com/content/paperback-book/visible-mantra-visualising-writing-buddhist-mantras/10070917
But it will take a little while to re-appear in my Lulu 'author spotlight'.