Having finished a degree in Electronics I would recommend the following two books:

* Engineering Maths by K. Stroud http://www.amazon.co.uk/Engineering-Mathematics-6th-K-Stroud... to my mind there's no better maths book, very logical step by step approach to improving maths skills by building on previous knowledge

* The Art of Electronics by Horowitz and Hall http://www.amazon.co.uk/Art-Electronics-Paul-Horowitz/dp/052... this is often referred to as the bible of electronics and acts as a great reference book (there is a circuit chip designer in my workplace who came from a physics background and taught himself electronics with this book)