Yes, it can be. It provides the most magical power of any item at full stacks. However, it takes time to build those stacks, and so you can fall behind with it if you're not careful. It's a really strong item to have in the end game though. Recently, matches have been ending too early on average to get full use out of it. With the most recent patch, health for all gods was increased by a significant amount, so matches might last longer. If they do start to last longer, Book of Thoth could be a great item to get. In that case, it would take the spot of Spear of Desolation in most of the builds here.