Funny, I was going to bring this up earlier today.
I would also guess that there's some combination. With Taylor having a credit on every song, he probably wrote some of the lyrics for each one. But there are some that seem very much like Steve lyrics, like, as Maturin said, the reference to a father in The Eyes of the Young seems very much like Steve's words, as he referred to his father on at least two occasions in Maiden songs (The Educated Fool, Blood Brothers). But some seem, as some have said, more personal than Steve's usual type (even on The X Factor, the most personal Maiden album, The Unbeliever and Judgement of Heaven were really the only personal lyrics by Steve, as the lyrics to Look for the Truth and 2 AM were written by Blaze), which would suggest that Taylor wrote them.
Easily the most common songwriting combination on the album is Harris/Taylor/Hawkins (Hawkins is one of the guitarists). There are only 3 songs that deviate: The Chosen Ones (Harris/Taylor), A World Without Heaven (Harris/Taylor/Roberts/Leslie/Fitzgibbon/Liederman) (that one includes current and former band members as well is someone who was never a band member but is listed in the acknowledgements of Grahame Leslie, IIRC), and Eyes of the Young (Harris/Taylor/Leslie/Roberts).
These credits also seem to suggest that since this has been an ongoing project, Richard Taylor (though you may not like him) has been with the band almost from the beginning, as has David Hawkins.