The Necroscope Lost Years series fills in some of the gaps over 2 books. Simply titled Necroscope: The Losy Years (I & II). Not much of a read and a bit boring for my liking. I bought them purely for the collection. You wont miss anything important if you don't read them.
Plot ***Spoilers***
Book I
Between Wamphyri! and The Source, earlier novels in Brian Lumley's internationally best-selling series of the millenia-long struggle of humanity against the most horrific plague of vampires ever spawned, the Necroscope harry Keogh searched for his lost wife and child for several years. Now the enthralling story of what the Necroscope believes happened during that time - and of what did happen - can be told.
It is a story that goes back to the earliest days of the vampire infestation of Sunside/Starside, a parallel world on the 'other' side of space time. Punished by Shaitan the Unborn for taking sides against him in the first bloodwars, several great Lords of the Wamphyri were banished through the 'Gate' on Starside - to Earth! Among these expelled Lords was the dog-Lord Radu Lykan, whose vampire leech was inherited from a wolf. So Radu is not only Wamphyri: he's also a werewolf. And it is he who, after centuries of suspended animation, is now on a collision course with none other than Harry Keogh...
Book II
They came between Wamphyri! and The Source, earlier novels in Brian Lumley's internationally best-selling series of embattled humanity's struggle against the most horrific plague of vampires ever spawned. From the Necroscope Harry Keogh's point of view, the missing years were empty, dead - or perhaps undead? Under mental restrictions imposed by E-Branch, beguiled by Bonnie Jean Mirlu, a fledgling Lady of the Wamphyri, Harry is a man of two minds, a split personality. But more than this - as a man revitalized in another man's body - he is the classic schizophrenic.
On the other hand, Radu Lykan is a man - or a monster - of two worlds. An original Lord of the Wamphyri, from Starside in an alien vampire world, Radu has lain preserved in resin in a state of suspended animation in his high Cairngorms lair for six-hundred years! Now the time of his return is at hand. Except -
- The dog-Lord has dreamed of a 'Man With Two faces' who will be there in the hour of his resurgence. Harry Keogh is that man, in whom Radu will rise up again, resurrected! Problem enough for the Necroscope, without that other vampire survivors - the last Drakul, and the Ferenczys - are also after his blood...