Looking to expand my knowledge

As my pracitce is becoming slightly more established I am attracting some larger clients that are beginning to stretch some of my tax knowledge so I think I need to brush up on some things I haven't looked at for a while/possibly ever!  I am ACCA qualified and sat the advanced tax paper but that was a good few(!) years back so wasn't sure whether its worth looking at the ATT perhaps?  Or alternatively will reading through something like Tolleys Tax Wise I & II be more beneficial to me?  Or is there something else I should be looking at that has slipped under my radar.

Many thanks.